Perimeter = 2 (W + H)
So....we have this
2 ( W + H) < 180 sub in for the width
2 ( 26 + H) < 180 divide both sides by 2
26 + H < 90 subtract 26 from both sides
H < 64 in
So....for the perimeter to be less that 180 in, the height must be less than 64 in