ok, your first step is fine
Solve the system of equations
5x-2y=16
15x-7y=51
Enter answer as ordered pair (x,y).
This is what I did:
-3(5x-2y=16)
-15x+6y=-48
15x-7y=51
so far so good :)
I am going to sid track for a bit
You know that 24 = 2 dozen
and you know that 7 = 21/3
these are completely unrelated facts but from this knowledge I can say 24+7 = 2 dozen + 21/3
Think very hard about what I have done. I added the left sides and that will = the sum of the right side.
So
you have
-15x+6y=-48
15x-7y=51
these are 2 independent facts
Add the left sides and that will equal the sum of the right sides
-15x+15x+6y+-7y = -48+51
-1y=3
y=-3
Now you know that y=-3 just sub it into one of the original equations to get x
5x-2y=16
5x-2*-3=16
5x+6=16
5x=10
x=2
so I have x=2 and y = -3
I have substituted them into both original equations to check and they work just fine.
Your second question you have asked is almost identical. Just easier.
https://web2.0calc.com/questions/consider-the-system-of-equations_2
Learn from what I have written and try answering it for yourself