For 6m+9n≡0(mod5):
6≡1(mod5) and 9≡−1(mod5)
So 6m+9n≡1+(−1)n(mod5)
This equals 0 only when n is odd.
Number of odd n in {1,...,50} = 25, and m can be any of 50 values.
p=50×25=1250
For m+n = square of prime, possible values are 4, 9, 25, 49.
m+n=4: 3 pairs
m+n=9: 8 pairs
m+n=25: 24 pairs
m+n=49: 48 pairs
q=3+8+24+48=83
p+q=1250+83=1333