Remark
The area = 4*(x + 3) to start with. If you remove the brackets,
A = 4(x + 3)
A = 4*x + 3*4
A = 4x + 12 <<<<<< Answer for A
Part B
The area will become 4 times larger.
A = 4*(4x + 12)
A = 16x + 48
Argument
You may not be wholly satisfied with an unproved statement. I could prove it with algebra but it might be easier just to give an example.
Area = L * W
L = 10
W = 5
Area = 10*5
Area = 50
Now double both L and W
L = 20
W = 10
Area = L*W
Area = 20*10
Area = 200 which is 4 times the size of 50.
