Answer:
B
Explanation:
Our system of equations is:
3x + y = 23
8x + 2y = 23
If we want to use substitution, that means that we essentially want to manipulate one of the two equations so that one variable (like y) is written in terms of the other (like x), and then substitute that expression into the second equation so that we have one variable and one equation and we can easily solve from there.
So the first thing to be done is to write one of the variables in terms of the other. It would be easiest to do it with the first equation and write y in terms of x - in other words, "solve the first equation for y".
The answer is B.