x= 6√5
1) Considering the right triangle metric relations and examining the picture, in which we're looking for the altitude of the triangle. Let's pick the one for the height of the right triangle and the projections of the hypotenuse: 20,9
h²= m.n In this triangle we can rewrite it as
x²=20*9
√x²=√180
x=6√5, and -6√5 The negative value does not fit into that
So, x= 6√5