You have a square that was has a length of 2.
It underwent an operation to become two.
It was created from another square that had a side of x units long.
The relationship between the child square and the parent square is 1/2.
The side of the child is 1/2 as big as the parent [As far as I know parent and child are actual terms].
So let the Parent's side = P and let the child's side = 2 (given)
1/2 P = 2 Multiply both sides by 2
2(1/2 P] = 2*2
P = 4
The parent's side is 4 which is also the answer.