3x + 7 − 7 = 22 − 7 → 3x = 15
🎁 Free starter lesson · No signup required
Start Here: Solving a Linear Equation
A free 3-step lesson from Dr. E. Watch a short clip, walk through one worked example, then try a practice problem on your own. Nothing to install. No account to make.
Watch the lesson
A quick intro to how Dr. E breaks down a linear equation. Press play whenever you're ready.
Worked example: solve 3x + 7 = 22
Linear equations have one variable. Your job is to isolate that variable using inverse operations — one step at a time.
3x + 7 = 22
1
Subtract 7 from both sides to undo the +7.
2
Divide both sides by 3 to undo the multiplication.
3x ÷ 3 = 15 ÷ 3 → x = 5
3
Check by plugging x = 5 back in.
3(5) + 7 = 15 + 7 = 22 ✓
✓
The answer is x = 5. The equation is balanced.
Now you try
Use the same two moves: undo addition or subtraction first, then undo multiplication or division. Grab a piece of paper.
Solve for x:
5x − 9 = 16
Show the solution
1
Add 9 to both sides to undo the −9.
5x − 9 + 9 = 16 + 9 → 5x = 25
2
Divide both sides by 5 to undo the multiplication.
5x ÷ 5 = 25 ÷ 5 → x = 5
3
Check by substituting x = 5.
5(5) − 9 = 25 − 9 = 16 ✓
✓
The answer is x = 5. Nice work.