the distributive property is just using a certain type of grouping symbols inorder to distribute a particular operation to everything within that grouping symbol.
in the problem 2(a-2), you distribute the 2 to everything within the grouping symbols, giving you 2a-4 as your final evaluated answer. if they wanted you to solve, you set it to zero as such
2a-4=0
2a=4
a=2
