In following question, a number series is given with one term missing. Choose the correct alternative that will same pattern and fill in the blank spaces. -
3, 4, 7, 7, 13, 13, 21, 22, 31, 44,
A + B means A is the son of B; A - B means A is the wife of B; A x B means A is the brother of B; A ÷ B means A is the mother of B; and A = B means A is the sister of B. What does P + R - Q mean ?