To find a, you need to isolate/get the variable "a" by itself in the equation:
Multiply the inverse of 1/2, which is 2, to get rid of the fraction

a - 7 = 66 Add 7 on both sides to get "a" by itself
a - 7 + 7 = 66 + 7
a = 73
We need the question and answer choices for us to answer
I believe it's 12=0
Hope I helped! ( Smiles )