First, we know that both triangles already have 2 sides with equal ratios:
AC /RQ = 6/3 =2
AB/QP = 10/5 =2
Now, if RP = 4.5 we will have 3 sides with equal ratios:
CB / RP = 9/4.5 = 2
with this condition, both triangles will be similar by SSS.
Also if they have 2 sides with equal ratios and equal included angles.
m< R = 63
m