Which equation would have the restriction or x ≠ 5 on the solution?

If Orlando did not make the early withdrawal, the amount of money he supposed to have is,
                               F = $16,000 + 0.065($16,000)(8) = $24,320
While making the early withdrawal only earned him,
       F1 = (16,000) + (0.065)($16,000)(8) - $3,500 - ($3,500)(0.065) = $20,592.5
The difference of two amounts are $3727.5.