數學的問題!!!!!!!!!!!!!!!!!!!!!!!!!!

a. Let grandfather age be y.
Let Peter age be 1/4y.
1/4x+63=12+x
-3/4x=-51
x=17*4
x=68
68-63=5
So after 5 years timen will peter age be 1/4 of his grand father age.

b. Let grand father age be x.
Let peter age be x/18
x+12=x/18+63
18x+216=x+1134
17x=1134-216
17x=918
x=57
63-57=9
So 9 years ago was grandfather age18 times peter.

Only answer:
a.after 5 years.
b.9 years ago.

(a) Let x be the number of yrs
12 + x / 63 + x = 1/4
48+ 4x = 63 +x
x=5

(b)
Let X be the number of years
63-X = 18(12-X)
63-X = 216 - 18X
17X = 153
X= 9

笑死我的問題
哈哈.)

(a) Assume x years later, Peter's age will be 1/4 of his grandfather's age

12 + x = (63 + x) /4
(12 + x) * 4 = (63 + x) /4 * 4
48 + 4x = 63 + x
4x - x = 63 - 48
3x = 15
x = 5

(b) Assume y years ago, grandfather's age was 18 times Peter's
63 - y = (12 - y) * 18
63 - y = 216 - 18y
18y - y = 216 - 63
17y = 153
y = 9