To use substitution, we must isolate #x# on one of the sides in one of the equations. The first equation looks simple enough to manipulate and isolate #x#.
We can add #7y# to both sides of the first equation to get:
#x = 7y + 16#
Now, we can turn towards the second equation. We can first simplify the left side by adding the #x#'s ( #-3x# and #6x#) to make the second equation:
#3x = -3#
Although we could just solve for #x# here, we should use substitution. We can know replace #x# with the equal value #7y + 16# (from the first equation) to make the second equation:
#3(7y + 16) = -3#
Now we can solve the second equation from there by distributing, subtracting, and dividing:
#21y + 48 = -3#
#21y = -51#
#y = -51/21 = -17/7#
To solve for #x#, we can substitute our value for #y# into the first equation (#x = 7y + 16#) to get:
#x = 7(-17/7) + 16#
#x = -17 + 16#
#x = -1#.
Therefore, our final solution is #x=-1# and #y = -17/7#
