Answer
Option C is correct.
x, in the first equation is the best variable to solve for here.
Step-by-step explanation
3x + 6y = 9
2x - 10y = 13
To substitute, we can see that the first equation is perfect with all of the coefficents divisible by 3 and x is the most prime candidate for substitution because once we divide the first equation through by 3, x is the variable that becomes alone and easy to solve for.
3x + 6y = 9
Divide through by 3
x + 2y = 3
x = 3 - 2y (Solved for!)
We can then substitute this into the second equation to solve the entire system of equations for x and y.
Hope this Helps!!!