Answer
You can multiply the first equation by 4 and the second equation by 3.
You can multiply the first equation by 4/3.
You can multiply the first equation by 3.
Explanation
When solving a system of equations by elimination, you want to add or subtract the equations to "get rid" of a variable.
To do that, one of the variables in both equations have to have the same coefficient.
The first answer possible gives x the coefficient of 12 for both equations. You would get 12x+4y=52 and 12x-9y=39. You could subtract those equations to get 13y=13.
The second way gives x the coefficient of 4. You would multiply the first equation by 4/3 to get 4x+4/3y=52/3. You can subtract to get one variable, and then solve from there. Although, multiplying for 4/3 is annoying, so it's not suggested.
You can also "get rid" the the y. Multiply the first equation by 3 to get 9x+3y=39. You can add these equations. When you add 9x+3y=39 and 4x-3y=13 you get 13x=52.
If there is 2 digits and 7 numbers the combos would be:
1,1 2,1 3,1 4,1 5,1 6,1 7,1
1,2 2,2 3,2 4,2 5,2 6,2 7,2
1,3 2,3 3,3 4,3 5,3 6,3 7,3
1,4 2,4 3,4 4,4 5,4 6,4 7,4
1,5 2,5 3,5 4,5 5,5 6,5 7,5
1,6 2,6 3,6 4,6 5,6 6,6 7,6
1,7 2,7 3,7 4,7 5,7 6,7 7,7
Therefore there are 49 possible combinations :)
I think it is B. and the amount that they each need to pay is $1.13
The answer is the third one