8x + 5y = -105
3x + y = -21
The easier method would be insert the answer choices into the either of the equations to see if you receive a true statement.
For answer choice A. x=5, y=-29
3(5) + (-29) = -21
15 -29 = -21
-14 = -21 Produces a False statement, so we can eliminate answer A.
For answer choice B. x = 0, y= -21
3(0) + (-21) = -21
0 - 21 = -21
-21 = -21 TRUE Now see it also produces a TRUE for the other.
8(0) + 5(-21) = -105
0 - 105 = -105
-105 = -105 TRUE
Since answer choice B. x=0, y=-21 produces true statements for both systems our correct answer choice is B.
