If x + y = 8 and y − 3x = 7, then what is the value of y-x? Choose the correct choice from the following
A) 1 / 7	B) 3	C) 15	D) 15 / 2	E) 60 / 7

Rationale: x + y = 8 . . . equation 1 - 3 x + y = 7 . . . equation 2 adding both the equations - 2 x + 2 y = 15 = > y - x = 15 / 2 correct answer option d
Answer: D