2w + 2l = 98 (1)
l = 2w - 5 (2)
substitute for l in eqn (1)
2w + 2(2w-5) = 98
expand
2w + 4w - 10 = 98
simplify
6w = 108
w = 18
substitute in (2)
l = 36 - 5
l = 31
Check in (1)
36 + 62 = 98 - answer checks
w = 18, l = 31
If the perimeter of a rectangle is 98cm and its length is 5cm less than twice its width, what are the dimensions?