Math!!!!英方程!!!!!

你好～～～

以下答案只供參考，如有錯誤請多多指教～～

另外，為方便看，所以我設全部的未知數為 y，以分開乘號(x)。

1)4m+3分1=1又3分2-3分1m

Sol: 4m + 1/3 = 1又2/3 - 1(m)/3

4m + 1/3 = 5/3 - m/3

4m + m/3 = 5/3 - 1/3

13m/3 = 4/3

m = 4/3 x 3/13

m = 4/13

2)To use the internet service provided by company A,Mary has to pay $100 for installation fee , and the charge for unlimited internet connection is $150 per month.If she has paid $1 000 altogether,for how long has she used the internet service provided by company A?

Sol: Let the number of month that she can use the service be y.

100 + 150y = 1000

150y = 900

y = 6

So, she can use half a year.

3)Donna has three types of coins :$1 coins,$2 coins,$5 coins.The number of $1 coins is three times that of $2 coins. The number of $2 coins is 5 more than the number of $5 coins.The total value oF Donna's coins is $325.How many $2 coins does she have ?

Sol: Let the number of $2 coins she has be y.

1 x 3y + 2y + 5(y - 5) = 325

3y + 2y + 5y - 25 = 325

10y = 350

y = 35

So, she has 35 $2 coins.

4)Peter is 12 years old and his grandfather is 63 years old now.

a)After how many years' time will Peter age be 4分1 of his grandfather age?

Sol: Let the number of years be y.

12 + y = (63 + y) / 4

48 + 4y = 63 + y

3y = 63 - 48

y = 5

After 5 years, it will happen.

b)How many years ago was grandfather's age 18 times Peter's?

Sol: Let the number of years be y.

12 - y = (63 - y) / 18

216 - 18y = 63 - y

216 - 63 = 17y

y = 9

So, 9 years ago, grandfather's age was 18 times of Peter's.

希望以上解答可以幫到你～～～～～