Question

Let x △ y be defined by x △ y=x−5y. What is the value of 3 △  (−4)

Answer 1

$x\Delta y=x-5y\\\\3\Delta(-4)\qquad\text{put the values x = 3 and y = -4 to the expression x - 5y}:\\\\3\Delta(-4)=3-5(-4)=3+20=23$