Video Explanation

Text Explanation

(x + t)/2 = y

(x + t) = 2y

s = 2y

The average of s, x, and t is (s + x + t)/3. In terms of y, this equals (2y + 2y)/3 = 4y/3.

Alternatively, you can plug in values for s, x, and t. For instance, x = 2, t = 4. Therefore, y is 3 and s = 6. The average of the three numbers would be (2 + 4 + 6)/3 = 4. So when you plug in y equals 3 into the question, you are looking for an answer that produces 4. Answer: (D).