please help me find the missing side length

Answer:
The value of m = 6
Step-by-step explanation:
from the diagrams, ABC is similar to QRS
If length /AC/ is 4 and /QS/ is 10, then
10/4 = 2.5
This means triangle QRS is 2.5 larger than ABC
therefore, if length /RS/ = 15
/BC/ = 15/2.5 = 6
Therefore m = 6