In order to find the value of x, consider that triangles PQR and PST are similar. Then, you have the following equivalence:
PQ/PS = PR/PT
Where:
PQ = x
PS = 45m
PR = 16m
PT = 36m
replace the previous values of the length of the segments and solve for x, just as follow:
x/45 = 16/36 multiply by 45 both sides
x = (16/36)45
x = 20
Hence, the value of x is x = 20
