Question

1/9 = a / a + 24 solve for a

Answer 1

do you mean 1/9 = a /(a + 24) ?

just cross multiply! i.e. multiply the numerator of one side by the denominator of the other side

(1)(a+24) = 9(a)

solve for a.

Answer 2

a+24=9a
24=9a-a
24=8a
8a=24 Divided with 8
a=3

Cheking:

3/(3+24)=3/(27)= 3/(3*9)= 1/9