The answer is 56 hope this helps
Multiply the bracket by 1/2
1/2(2n +6)
cross out 2 and 2n and divide by 2.
cross out 6 and 2 and divide by 2
n+3
Answer is n+3
Lisa is incorrect although it is an odd number it is not composite. It only has itself and 1. Therefore its a prime number.
This is the definition for prime if you still dont understand.
A prime number is a whole number greater than 1 whose only factors are 1 and itself.
=> 8+x = 15 => x = 15-8=7