Find all possible values of x in the similar triangles pqr stu

If triangles PQR and STU are similar then PQ corresponds to ST and PR corresponds to SU. Therefore, PQ/ST=PR/SU

Considering that, PQ = 7-x, ST = 13-x, PR = x²+5 and SU = x² + 20

therefore, (7-x) / (13-x) = (x²+5) / (x²+20)

cross multiplying,

7x² + 140-x³+20x = 13x²+65-x³-5x

combining the like terms,

6x² + 15x - 75=0

solving for x,

x = 5/2 or - 5