For 2x + x = 15:
When adding Xs, you add the coefficient, or the number in front of x.
2x + x = 3x (Think of x as 1x.)
3x = -15
What we're going to do is divide both sides by 3.
3x ÷ 3 = x
-15 ÷ 3 = -5
x = -5
For x + 3 = 4x + 9:
First, we will subtract x from both sides:
3 = 3x + 9
Now we'll subtract 9 from both sides:
-6 = 3x
To get x by itself, we will divide both sides by 3.
-2 = x
Hope I could help!
