Sometimes the unknown x turns up on both sides of the equals sign:

We can't divide straight away, because there's an x term left and right. The trick is to get every x onto one side first. Take away the smaller x term — here 3x — from both sides, so the equation stays balanced and no x goes negative:

On the left, 5x - 3x = 2x; on the right the 3x cancels and we're left with 10. (That tidying-up is just collecting like terms.) Now the unknown lives on one side only:

From here it's an ordinary one-sided equation — exactly like the kind we met after expanding brackets. Subtract 2 from both sides, then divide by 2:

Always strip the smaller x term from both sides to gather the unknown on one side; then solve as usual.

See it balance

Think of the equation as a balanced scale: whatever you do to one pan you must do to the other. Step through removing the smaller x term from both pans, then the number, until a single x is left. Each Refresh gives a new example.

See it explained

Sal Khan works through an equation with the unknown on both sides, gathering the variable onto one side before solving.