Question 522012
x-9 and 3x and hypotenuse of length 3x+1. 

(x-9 )^2+(3x)^2=(3x+1)^2

x^2-18x+81+9x^2=9x^2+6x+1

x^2-24x+80=0

x^2-20x-4x+80=0
x(x-20)-4(x-20)=0

(x-20)(x-4)=0

x= 20 OR 4