One-step equations

An equation says two things are equal, and a letter like x stands for the number we do not yet know. To find x we get it on its own by undoing what has been done to it — using the inverse operation and doing the same to both sides. In x + 7 = 12, something is being added to x, so we subtract 7 from both sides: x = 12 − 7 = 5. Always check by putting your answer back in: 5 + 7 = 12. ✓ Adding when you should subtract is the classic slip.