Solving equations, step by step
Solving an equation means undoing whatever was done to x until it stands alone.
The question
x − 7 = 20
x − 7=20
x − 7=20
x=27
x − 7=20
x=27
x=27
- One thing was done to x: 7 taken away. So there is one thing to undo, and undoing it is the opposite operation.
- The 7 went on last, so it comes off first — and off BOTH sides, or the two halves stop being equal. 20 + 7 = 27.
- Check by putting it back: (27) − 7 = 20. It holds, so x = 27.
How it works.
- 01
One thing was done to x: 7 taken away. So there is one thing to undo, and undoing it is the opposite operation.
- 02
The 7 went on last, so it comes off first — and off BOTH sides, or the two halves stop being equal. 20 + 7 = 27.
- 03
Check by putting it back: (27) − 7 = 20. It holds, so x = 27.