ST = ST (Common)
RT = TQ (Given)
∠ RTS = ∠ SQT (Both 90°)
So, ∆ RTS ≅ ∆ QTS (By SAS congruency rule)
So, RS = QS (By C.P.C.T.)
=> 2x + 8 = 8x - 4
=> 8 + 4 = 8x - 2x
=> 12 = 6x
=> 12/6 = x
=> 2 = x
SR = 2x + 8 (Given)
=> SR = 2(2) + 8 (Putting the value of x)
=> SR = 4 + 8
=> SR = 12