3^a = (3^4)^(b + 2) (5^3)^b = 5^(a - 3) * (5^2)^b divide through by (5^2)^b
3^a = 3^(4b + 8) 5^b = 5^(a - 3)
a = 4b + 8 b = a - 3 (2)
a - 4b = 8 (1)
Sub (2) into (1)
a - 4 ( a - 3) =8
a - 4a + 12 = 8
-3a = - 4
a = 4/3
And
b = a -3 = 4/3 - 3 = -5/3
ab= (4/3)(-5/3) = -20 / 3
