Question 73618
Let's look at the general case, how to factor {{{a^3-b^3}}}.

By the binomial theorem, {{{(a-b)^3 = a^3-3a^2b+3ab^2-b^3}}}. 
So, {{{a^3 - b^3 = (a-b)^3 + 3a^2b - 3ab^2}}}.
Or, {{{a^3 - b^3 = (a-b)^3 + 3ab(a-b) = (a-b)((a-b)^2 + 3ab)) = (a-b)(a^2+ab+b^2)}}}.

So, for the problem at hand we substitute a=x and b=5 and we get

{{{highlight(x^3 - 5^3 = (x-5)(x^2+5x+25))}}}.