Last Updated on May 10, 2023
GMAT OFFICIAL GUIDE PS
Solution:
Although our first instinct may be to use the substitution method to determine the values for x and y, it will actually be more efficient to add together the two given equations of 2x + y = 7 and x + 2y = 5. When adding these two equations together we obtain:
3x + 3y = 12
Dividing the equation by 3 we obtain:
x + y = 4
We should notice that we are asked to determine the value of (x + y)/3. Since x + y = 4, then (x + y)/3 = 4/3.
Answer: B
Note: In any question in which we are asked to determine a value for an expression of two (or more) variables, such as the value of x + y in this question, we want to think of creative ways to determine the answer. As mentioned above, adding the equations together was more efficient than determining the values for x and y individually.
