Use the Pythgorean Thearom and find the hypotenuse remember a^2+b^2=c^2
divide RQ by 2 and divide PQ by 2 then use the Pythgorean Thearom to find ZX
Notice that \(\triangle RYX \sim \triangle XZQ\) by AA postulate.
Let x be the side length of the square. Then
\(ZQ = 12-x\\ RY=8-x\\ YX=x\\ XZ=x\)
By similar triangles,
\(\dfrac{RY}{YX} = \dfrac{XZ}{ZQ}\\ \dfrac{8-x}{x}=\dfrac{x}{12-x}\)
Solving this equation gives the required answer.
Ans: Side length = 24/5.
As an exercise, you can try to show that when PQ = a, PR = b, the side length of the square is \(\dfrac{ab}{a + b}\).