The larger triangle is 5x the size of the smaller triangle. 5*5=25 and 3*5=15 So I figured that would be the same for the 3x+8 side and the 4 side. 4*5=20, So you'd set 3x+8 equal to 20 and solve from there. 3x+8=20 -8 -8 [tex] \frac{3x=12}{3} [/tex] x=4