This question asks the following: "For all numbers q and r, the operation ☼ is defined by q ☼ r = (q + 3)(r - 2). If 1 ☼ z = -8, z is equal to which of the following?

The correct answer is D, which has z = 0. I'm confused about the use of words "the operation ☼ is defined by(...)." I imaged operation ☼ as the following: f(☼) = q ☼ r = (q + 3)(r - 2). Since we had 1 ☼ z = -8, I rearranged this equation and deduced that we're looking for z = -8/☼. In other words, I had to solve for the following to obtain z: -8/(q + 3)(r - 2). I was stuck at this point. After looking at the solution, I am still uncertain about the term "the use of operation ☼."

This is my understanding,

I thought that "the operation ☼ is defined by(...)." just gave the condition of the question.

Look at this question in this way.

q ☼ r = (q + 3)(r - 2).
1 ☼ z = -8

compare the left of the two equations.(notice the same colore signals)

It is clear that q=1, r=z, and (q + 3)(r - 2)=-8.

then put q=1, r=z into (q + 3)(r - 2)=-8

(1+ 3)(z - 2)=-8

thus z=0