Question 742012
Exponentiation first.  the 'a' is already taken care.  The b is part of a grouped expression which itself is to be exponentiated.  Work first with the -6b^3, which is given an exponent of 2.


{{{(-6)(-6)(b^3)*(b^3)}}}
={{{(+36)b^6}}}


Now you can partly simplify the given expression:
{{{(-5a^2)(-6b^3)^2}}}
={{{(-5a^2)(36b^6)}}}
Since all numbers, exponentiated and not, are present as factors, take advantage of associative property of multiplication - in fact no grouping symbols needed further, so,...
={{{-1*5a^2*36b^6}}}
Take advantage of commutative property of multiplication, and get...
={{{-1*5*36*a^2*b^6}}}
={{{highlight(-180a^2*b^6)}}}