First, distribute 2 to the (x+3) to get:
21 = 2x+6
subtract 6 from both sides to get:
15 = 2x
Finally, we divide both sides by 2 to simplify x to:
x = 7.5 (OR) x =
(Just so you know, if you pick a brainliest answer, both you and the person who got the brainliest answer get some points.