Digital PSAT Math Practice Question 242: Answer and Explanation

Question: 242

Given that (x, y) is a solution to the following system of equations, what is the sum of x and y?

2x - y = 3

4y = 6x

Correct Answer: 15

Explanation:

15 Solve the second equation for y to solve this system of equations using substitution.

Next, plug in for y in the first equation:

. In order to combine the x terms, you need a common denominator: , so our equation becomes . Dividing both sides by tells you that x = 6. Next, plug in 6 for x in the equation that you already solved for y: . Since x = 6 and y = 9, their sum is 6 + 9, or 15.