for gas a you do -21 - -8 which would equal -29 because if they are both negatives they add to each other but are still negative
Her brother is 7 years old at the moment. He will be 21 when his sister is 36.
Answer:
A Exactly one solution
Step-by-step explanation:

Putting y=0 at second equation, we have

The unique solution is 
3.9 and thatis the answer