X - Ollie's age
8 is subtracted from Ollie's age = x-8
the result is the same as
subtracting 16 from 3 times his age = 3x-16

Ollie is 4 years old.
0 solutions
move the x to one side, and the numbers to the other.
12x (-12x) + 32 (-32)= 12 (-12x) - 7 (-32)
12x - 12x = -7 - 32
0 = -39
0 ≠ -39
∴ you have 0 solutions
hope this helps
Account 1 : y = 2500(1.078)x
account 2 : y = 2500 + 300x
after the second year a1 exceeds a2
after 2 years, a1 = 5390
after 2 years , a2 = 3100