Question 581543
Old rectangle:

L = 2W 

New rectangle:

L+3, W+3

Perimter:

P = 2(L+W) = 2(2W+3 + W+3) = 4(2W) + 2

2(3W+6) = 8W + 2

6W + 12 = 8W + 2

2W = 10

W = 5

original dimensions:  10 x 5

CHECK:

Old rectangle: 10 x 5
New rectangle: 13 x 8

P(new) = 2(21) = 42 = 4(10) + 2 √