Adding the equations side-by-side eliminates y, as shown below. 7x+3y=8 6x−3y=5 –––––––––– 13x+0=13 Solving the obtained equation for x gives x=1. Substituting 1 for x in the first equation gives 7(1)+3y=8 Subtracting 7 from both sides of the equation yields 3y=1, so y=
1
3
Therefore, the value of x−y is 1−
1
3
, or
2
3
Choice C is incorrect because 1+
1
3
=
4
3
is the value of x+y, not x−y. Choices A and D areincorrect and may be the result of some computational errors.