I'll do a similar problem, and I challenge you to do this on your own using similar methods!
x+5y+2z=23
8x+4y+3z=12
9x-3y-7z=-10
Multiplying the first equation by -8 and adding it to the second one (to get rid of the x) and also multiplying the first equation by -9 and adding the third one to get rid of the x there too, we end up with
-36y-13z=-92
and
-48y-25z=-217
Multiplying both equations by -1, we get
36y+13z=-92
48y+25z=217
Multiplying the (new) first equation by -4/3 and adding it to the second (to get rid of the y), we get
(7+2/3)z=94+1/3
Dividing both sides by (7+2/3) to separate the z, we get
z=

Plugging that into
48y+25z=217, we can subtract 25z from both sides and divide by 48 to get

Lastly, we plug this into x+5y+2z=23 to get
x=23-5y-2z by subtracting 5y+2z from both sides to get
Good luck, and feel free to ask with any questions!
Can you post the rest of the question?
Something along the lines of multiplying and adding
What's the actual problem?
Answer:
$7.50
Step-by-step explanation:
Just subtract.