since ΔQRS similar to ΔQRP, then
SR/QR = QR/PR
x/12 = 12/(3.5+x)
x(3.5+x) = 12²
x² + 3.5x = 144
x² + 3.5x - 144 = 0

approximately 10.38
What do you mean, the answer is 12 and we know that because we combine the numbers
The product of p and 9 mean 9*p so 9p so the 3rd choice is right sure