Answer:
4(7+3x)
Explanation:
We know that a square has all equal sides, otherwise it's not really a square. So if each side of the square is 7+3x units, then the perimeter (which is always side+side+side+side) would be 4 times as great. In other words, since the perimeter is side+side+side+side, and since that multiplication is repeated addition, 4(7+3x) is the same as (7+3x)+(7+3x)+(7+3x)+(7+3x)