數學問題！超急！（不會英文的抱歉@@下面的全是英文）

1. 80%(10＋62.5%y)÷5.5=(2y ﹣8)÷11
80%(10＋62.5%y)*11=(2y ﹣8)*5.5
80%(10＋62.5%y)*2=(2y ﹣8)
(4/5)(10＋62.5%y)*2=(2y ﹣8)
(4/5)(10＋62.5%y) = y - 4
(4)(10＋62.5%y) = 5(y - 4)
40 + 2.5y = 5y - 20
2.5y = 60
y = 24

2.Mr. White buys some toys at $960. If he sells them at $8 each, he will get his sum of money back by selling 40% of them. If he sells all of them, what will be the profit percentage?
Let n be the total number of toys bought.
40%(n)*8 = 960
n = 300
If he sells all of them, he can get $8*300=$2400
His profit would be $2400 - $960 = $1440.

3.A coin with diameter 21mm and thickness 3mm is painted with black ink on its rim. Then it is rolled on a paper so that a thin rectangle is drawn. If the area of the rectangle is 1980mm², find how many turns has the coin rotated.
(Take π is 7分之22)
The perimeter of the coin is 2*π*radius = 2*(22/7)*(21/2) = 66 mm.
The length of the ink rectangle is 1980/3 = 660 mm.
Therefore, the number of turns is 660/66 = 10.

不會英文的抱歉@@下面的全是英文...
你激起我.對我自己英文程度的了解
那些英文看起來還蠻簡的馬.哈哈(誤)