The answer is C. x, in the first equation. The first equation is easiest to simplify since other than 8y is their common variable, equation 1 is also divisible by 2 so it will not contain any fractions which would be harder to simplify.
Rearranging the first equation, the result would be:
2x + 8y = 12 8y = 12-2x----equation 1
This equation can then be directly substituted to the second equation since the value of 8y is given.
Substitute the right hand of the first equation of 8y which is 12-2x to the second equation. The result would be:
