MMati Learning Hub

TOPIC 5 · GRADES 3–4

Missing Numbers and x

Find an unknown value and keep both sides of an equation equal.

BIG IDEA

The equal sign means both sides have the same value. Undo an operation with its inverse to isolate the unknown.

WHAT TO KNOW

  • A letter such as x is a placeholder for an unknown number.
  • Addition and subtraction undo each other; multiplication and division undo each other.
  • Substitute the answer back into the original equation to check it.

WATCH OUT

The equal sign does not mean “the answer comes next”; it means the two expressions balance.

TRY IT

Move the value of x and watch the balance become equal or unequal.