Answer:
I think 12 is the answer
Explanation:
In ∆ QOP
R and S is the midpoint of OQ and PQ
and RS is parallel to OP
Therefore , By BPT
∆QRS is similar to ∆ QOP
let QS length be 1 unit
therefore , QP is 2 unit ( because QS is half of QP )
RS / OP = QS / QP
18-4x / -9+7x = 1 / 2
after cross multiplying
36-8x = -9+7x
36+9 = 7x+8x
45 = 15x
x=3
we have OP length = -9+7x
put the value of x in above equation
-9+7×3
-9+21
12