25ⁿ ⁻ ³ = 5ⁿ ⁺ ⁸
Make both bases to be equal.
Recall 25 = 5²
(5²)⁽ⁿ ⁻ ³⁾ = 5ⁿ ⁺ ⁸
5²⁽ⁿ ⁻ ³⁾ = 5ⁿ ⁺ ⁸
2*(n - 3) = 2*n - 2*3 = 2n - 6
5²ⁿ ⁻ ⁶ = 5ⁿ ⁺ ⁸
Since the bases which is 5 are equal, that means the powers are the same.
2n - 6 = n + 8, take the n to the left side of the equation
2n - n = 8 + 6
n = 14
I hope this helps.