Jon has to choose which variable to solve for in order to be able to do the problem below in the most efficient manner.

6x + 3y = 27 5x+ 2y + 21

which variable should he choose so that he can use substitution to solve the system?
jon should solve for y in the first equation because the coefficients can be reduced by a common factor to eliminate the coefficient for y.
jon should solve for x in the first equation because the coefficients can be reduced by a common factor to eliminate the coefficient for x.
jon should solve for y in the second equation because the coefficients can be reduced by a common factor to eliminate the coefficient for y.
jon should solve for x in the second equation because the coefficients can be reduced by a common factor to eliminate the coefficient for x.