Answer: 4mm
Explanation:
[tex]88 = \cfrac{1}{2}x(x+40)[/tex]
[tex]88 = \cfrac{1}{2}x^2 + 20x[/tex]
[tex]x^2 + 40x - 176 = 0[/tex]
[tex](x + 44)(x - 4 )=0[/tex]
[tex]x = -44 \ or \x =4[/tex]
[tex]x = 4[/tex]
The Wise Orange knows that height cannot be a negative value.