Answer:

Explanation:
step 1
Find the value of x
we know that
r is the midpoint of qs
so
QR=RS
QS=QR+RS------> QS=2RS -----> equation A
RT=RS+ST ----> equation B
see the attached figure to better understand the problem
Substitute the given values in the equation B and solve for x





step 2
Find the value of RS

substitute the value of x


step 3
Find the value of QS
Remember equation A
QS=2RS
so
