I literal interpretation of the Zoemoe's question would suggest that n = 250 - 5% = 249.95. But that seems to be an unlikely interpretation.

(Zoemoe: correct me if I'm wrong.)

XOR's interpretation of "n + 5%" is "n plus 5% of n", which is n*(1+5%) = 250. So n = 250/(1+5%), which is 238.095238095238. That seems to be a likely interpretation, IMHO.

I cannot imagine any interpretation of "n + 5% = 250" that would lead you to think it means: n + 250/(1+5%) = 250, which leads to your solution: n = 250 - 250/(1+5%).

Please explain your interpretation in English(-like) terms.