Step 1) Because the second equation is already solved for yy, substitute 5x + 275x+27 for yy in the first equation and solve for xx:
9x - 9y = -279x−9y=−27 becomes:
9x - 9(5x + 27) = -279x−9(5x+27)=−27
9x - 45x - 243 = -279x−45x−243=−27
-36x - 243 = -27−36x−243=−27
-36x - 243 + color(red)(243) = -27 + color(red)(243)−36x−243+243=−27+243
-36x - 0 = 216−36x−0=216
-36x = 216−36x=216
(-36x)/color(red)(-36) = 216/color(red)(-36)−36x−36=216−36
(color(red)(cancel(color(black)(-36)))x)/cancel(color(red)(-36)) = -6
x = -6
Step 2) Substitute -6 for x in the second equation and calculate y:
5x + 27 = y becomes:
(5 xx -6) + 27 = y
-30 + 27 = y
-3 = y
y = -3
The solution is x = -6 and y = -3 or (-6, -3)
