How do I solve this system of questions?

Question

The length of a rectangular garden is four more than three times the width, if the perimeter of the garden is 104 feet, then what are the dimensions?

Answer 1

L=4+3W Length = 4 more than 3 times the width

Perimeter = 104 = 2L + 2W substitute first equation into the 2nd

104 = 2(4+3W) + 2W = 8 +6W + 2W = 8 + 8W

8W = 104-8 = 96

8W = 96

W = 96/8 = 12 feet

L=4+3W = 4+3(12) = 40 feet

Dimensions are 12 x 40 feet