Answer:
x = 15 or x = -19
Step-by-step explanation:
ΔPQR similar to ΔSQT
SQ / QP = ST / PR
8 / 8+x+5 = x-9 / 21
8 / 13+x = x-9 / 21
(x+13)(X-9) = 168
x² + 4x - 117 = 168
x² + 4x - 285 = 0
(x - 15) (x + 19) = 0
x = 15
x+13/9 = 21/x-9
x^2+4x−117=168
x^2+4x−285=0
(x−15)(x+19)=0
x=15
it cannot be a negative number so x cannot be -19
