If you just plow ahead without thinking, you might try to answer this question
by solving for one variable at a time. That would work, but it would take a lot
more time than this question needs. As usual, the key to this simultaneous
equations question is to combine the equations, but combining the equations
doesn’t necessarily mean losing a variable. Look what happens here if you just
add the equations as presented:
Suddenly you’re almost there! Just divide both sides by 3 and you get x + y = 1.
The answer is (C).
ABSOLUTE VALUE
To solve an equation that includes absolute value signs, think about the two
different cases. For example, to solve the equation |x − 12 | = 3, think of it as
two equations: