Which of these shows the result of using the first equation to substitute for y in the second equation, then combining like terms? y = 3x 3x + 2y = 18

This problem calls for a simple substitution. We need to substitute 3x in for y in the equation 3x + 2y = 18 and then simplify by combining like terms.

3x + 2y = 18

y = 3x

3x + 2(3x) = 18

3x + 6x = 18

9x = 18

Now, if you want to solve for x, just divide both sides by 9 and simplify:

9x / 9 = 18 / 9

x = 2