Question 204654
a=Ann's age
b= Bill's age

a= (7/10)b = (7b)/10

in four years means

a + 4 = (8/11)(b+4)

now we know what a is in terms of b, we just plug it into the formula above

(7b)/10 + 4 = (8b)/11 + 32/11

solve for b

(7b)/10 + 4 = (8b)/11 + 32/11
-(7b)/10 on both side
-32/11 on both side
_____________________________
12/11 = (3/110)b
times 110/3 on both side
_________________
40 = b

Bill's age is 40.