1.兩個數字種較大的那個是較小那個的兩倍還多1。這兩個數之和比較大數的3倍少20。求這兩個數。
設較大數為x，較小數為y
x=2y+1，x+y=3x-20
解得x=13 y=6
2.The price of a sweater is $5 less than twice the price of a shirt. If four sweaters and three shirts cost $200, find the price of each shirt and each sweater.
2.壹件毛衣的價格比壹件襯衫價格的兩倍少5塊錢。如果4件毛衣和3件襯衫壹***200塊，求每件毛衣和襯衫的價格。
設毛衣價格x，襯衫價格y
x=2y-5，4x+3y=200
解得x=35 y=20
3.A shipment of TV sets, some weighing 30kg each and the others weighing 50kg each, has a total weight of 880kg. If there are 20 TV sets all together, how many weigh 50kg?
3.運送壹批電視，有的每臺重30KG，其他的每臺重50KG，這批電視的總重量是880KG。如果壹***有20臺電視，其中有多少臺重50KG？
設X臺重30KG的，Y臺重50KG的
30x+50y=880，x+y=20
解得x=6 y=14
4.A scholarship fund raised $7000 in contributions.Part was invested in bonds paying 6% interest, and the rest was invested in bank certificates paying 8.5%, If the total annual income is $520, find the amout invested at each rate.
4.壹項基金總***募集到7000元。壹部分投資於可獲得6%利息的債券，其他投資於利息8%的bank certificates。如果總***的年收入為520元，求每壹項的投資額。
設債券投資x元，bank certificates投資y元
x+y=7000, 0.06x+0.085y=520
解得x=3000 y=4000
5.Dr.D.Jones has a total of $3000 invested in two stocks. Stock A pays dividends at the rate of 6% and Stock B at the rate of 8%. If her dividends from the two stocks total $220 per year, how much did she invest in each stock?
瓊斯醫生總***投資3000元在兩只股票上。股票A分紅為6%，股票比分紅為8%。如果她每年獲得的總分紅為220元，她在每只股票上的投資額是多少？
設股票A投資x元，股票B投資y元
x+y=3000
0.06x+0.08y=220
6.A boat travels 60km upstream(against the current) in 5 hours. The boat travels the same distance downstream in 3 hours. What is the rate of the boat in still water? What is the rate of the current?
6.壹條船以60KM逆水行駛5小時。同樣的距離順水行駛只需要3小時。求船在靜水中的速度和水速。
設船靜水速度為x，水速為y
x-y=60，(x+y)*3=60*5
7.On an upstream trip, a canoe travels 40km in 5hours. Downstream, it travels the same distance in half the time. What is the rate of the canoe in still water and the rate of the current?
7.逆水航行，獨木舟以40km行駛了5小時。順水航行相同的距離只用了壹半的時間。求獨木舟在靜水種的速度和水速。
設船在靜水中速度x，水速為y
x-y=40，(x+y)*(5/2)=40*5
8.When a plane flies with the wind, it can travel the same distance in 5hours. Find the rate of the plane in still air and the rate of the wind.
8.題目不全啊
9.A duck can fly 2400m in 10min with the wind.Against the wind,it can fly only two thirds of this distance in 10min. How fast could the duck fly in still air? What is the rate of the wind?
9.壹只鴨子順風飛2400m需要10分鐘，逆風的時候10分鐘只能飛2/3的距離。鴨子無風飛行速度多少？風速多少？
設鴨子無風飛行速度x，風速y
(x+y)*10=2400
(x-y)*10=2400*2/3
10. When lucy swims with the current, she swims 18km in 2hours. Against the current, she can swim only 14km in the same time. How fast can lucy swim in still water?What is the rate of the current?
10.Lucy順水遊18km需要2小時，逆水相同的時間內只能遊14km。求lucy靜水中的速度和水速
設lucy靜水中的速度x，水速y
（x+y)*2=18
(x-y)*2=14
11.With the wind, a plane flew 1400km in 4 hours. On the return trip, the pilot was forced to land after 1h 30min, having traveled only 450km. Find the rate of the plane in still air and the rate of the wind.
11.飛機順風飛1400km需要4小時，返航時，飛行員在1小時30分之後迫降，只飛了450km。求飛機無風時的速度和風速
12.With the wind, a jet can fly 2500km in 2h 30min. Against the wind, it can fly only 2000km in the same time. Find the rate of the jet in still air and the rate of the wind.
13.A salmon swims 100m in 8 min downstream. Upstream, it would take the fish 20min to swim the same distance. What is the rate of the salmon in still water?What is the rate of the current?
這12題我都有答案，妳們幫我寫式子就行了，記住要用2個未知數來代表，
答案：
1.13,6
2.sweater:$35, shirt:$20
3.14
4.3000-6%, 4000-8.5%
5.Stock A-1000,Stock B-2000
6.Boat-16, current-4
7.12,4
8.550-plane,50-wind
9.duck-200meter/min, wind-40
10.8,current:1
11.325-plane,25-wind
12.jet-900,wind-100
13.salmon-8.75, current-3.75