Plug in 3 for y
3x + 6y = 24
y = 3
3x + 6(3) = 24
3x + 18 = 24
Isolate the x. Note the equal sign. What you do to one side, you do to the other. Do the opposite of PEMDAS.
Subtract 18 from both sides
3x + 18 (-18) = 24 (-18)
3x = 24 - 18
3x = 6
Next, isolate the x by dividing 3 from both sides
3x/3 = 6/3
x = 6/3
x = 2
x = 2, or A), is your answer
hope this helps