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.
Step-by-step 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.