1) you have the units confused. Perimeter is units of length, area is units of length squared. Assuming the perimeter is 60 inches (not squared) then:
L = 18
2L+2W = 60
2(18) + 2W = 60
W = (60 - 36)/2 = 12
2) L = W+26
2L + 2W = 136
2(W+26) + 2W = 136
4W = 136 - 2*26 = 136 -52 = 84
W=84/4 = 21
L = 18
2L+2W = 60
2(18) + 2W = 60
W = (60 - 36)/2 = 12
2) L = W+26
2L + 2W = 136
2(W+26) + 2W = 136
4W = 136 - 2*26 = 136 -52 = 84
W=84/4 = 21