Two equations, two letters, and one pair of numbers that satisfies both. These free printable worksheets practice getting from two unknowns down to one.
If they get stuck
The answer key prints on a separate page.
Both methods on these sheets do the same thing, and a child who sees that has understood the topic. Two equations with two unknowns cannot be solved as they stand, so the first move is always to produce one equation with one unknown. Elimination cancels a letter by adding the equations; substitution replaces a letter with what it already equals. After that step, both are an equation the child has already met.
Adding two equations together is the part that looks like a trick, and it is not. Both sides of each equation are equal, so adding the left of one to the left of the other — and the right to the right — keeps the balance. It is the same move as adding 3 to both sides, done with a whole equation instead of a number.
One question from a sheet like this one, worked a step at a time — with a sentence saying what just happened and why.
Systems of equations, step by step