Answer:
B) 15/(9+(-9))
Step-by-step explanation:
Be careful of the parentheses because if you just write out 15/9+(-9),
it's technically, saying that 15/9+(-9)=5/3+(-9)=5/3-9, and that's different from what you want to express, mathematically.
Answer:
3 79/100
Step-by-step explanation:

Answer:
a=6 or -6
Step-by-step explanation:
Solve the determinant to get a²-36=0
(a-6)(a+6)=0
a=6 or -6