Question

Which ordered pair is the solution to the system of equations?
2x+y=-8
x-y=-4

A.
(−3, −2)

B.
(−1, 3)

C.
(1, 5)

D.
(−4, 0)

Answer 1

I don't recommend short cuts for multiple choice questions, because real problems in life are seldom multiple choice questions.
However, for this particular type of problem where we're given multiple answers to a system of equations, instead of checking one equation at a time, I would add the equations together and in this case, I would check the sum, equation (3) against the answer choices.
2x+y=-8...(1)
x-y=-4......(2)
(1)+(2): 3x=-12 ........(3)
or x=-4

There is only one answer choice that gives x=-4, so I would go for it, and check that answer choice against each of equations (1) and (2).
This is especially time-saving for the systems of more than two variables.