Question 144866
You can apply the binomial expansion to this:
{{{(a+b)^3 = a^3+3a^2b+3ab^2+b^3}}} 
In your problem, a = x and b = 5, so...
{{{(x+5)^3 = x^3+3x^2(5)+3x(5)^2+5^3}}} Simplifying this, we get:
{{{(x+5)^3 = x^3+15x^2+75x+125}}}