If you are wondering how you can make sure that your answer is right, you can always check your answer by putting the number that n equals in the original equation.
Let's put rosala's n = -2 in to make sure it works!
10(11n+5)=-10n-10+90n
10(11(-2)+5)=-10(-2)-10+90(-2)
10((-22)+5) = (+20)-10+(-180)
10(-17) = 20-10-180
-170 = 10-180
-170 = -170
This is a true statement, -170 does equal -170, so we know the answer is right.
Anyway, hope this helped.