A triangle plus a triangle makes ten, so a triangle is five. These free printable puzzles hide the same number behind the same shape and ask a child to read it back out, which is solving for an unknown before anyone has called it x.
If they get stuck
The answer key prints on a separate page.
A symbol puzzle is an equation in disguise, and that disguise is exactly what makes it useful. A child who is not yet ready for letters will happily reason that if two of the same shape make ten then one makes five — and that is precisely the move that x will later ask for. The notation is doing the intimidating, not the mathematics.
The harder puzzles chain the shapes: once the triangle is known, a triangle plus a circle making eight tells you the circle. Working out the shapes in the right order — the one you can find first, then the one it unlocks — is the reasoning the page builds, and it is the same order of operations a system of equations needs.
One question from a sheet like this one, worked a step at a time — with a sentence saying what just happened and why.
Symbol puzzles, step by step