Answer:
A Exactly one solution
Step-by-step explanation:

Putting y=0 at second equation, we have

The unique solution is 
The answer is definitely 31
Answer:
B or the third option you put.
Step-by-step explanation:
Answer:
Step-by-step explanation:
Number of boys = g - 7.
g - 7 + g = 23
2g = 30
g = 15.
The are 15 girls in the class.
I think that using the elimination method is the best, because it is the only method that I use when solving these types of equation. For example, for these two equations, you need to multiply one of the equations by a certain number so that you'd be able to find x and y. The elimination method is the method that tells you to do that. It is also the easiest method.
~Hope I helped!~