15+32=47. 180-47=133. answer=133
I am sorry for my bad hand writing

This is the solution of the equation, where a=1, b=-5, c=7
So the discriminant is :
b^2-4ac=25-4*7= -3
The square root of -3 is non-real, this both solutions are non-real.
The plane would be 100 feet long. if the scale is 1/100 and the model is 1 ft you would take 1 x 100 to get 100 feet.