The correct option is C p=12,q=11
12+(8+11)
Using associative property of addition, we get
12+(8+11)=8+(12+11)
Using commutative property of addition, we can write 12+11 as 11+12.
⇒12+(8+11)=8+(12+11)=8+(11+12)=8+(p+q) (given)
∴p=12,q=11 or p=11,q=12