Sign rule: cross the =, flip the sign

Sign Flip Math

Practice simple equations with one blank. Every number is under 30, and the missing answer is always from 1 to 20.

When a number jumps across
x + 7 = 15 x = 15 - 7
Minus changes too
18 - x = 6 -x = 6 - 18

Quick Reminders

Use these every time you solve a problem.

Move + 5 across = and it becomes - 5.
Move - 4 across = and it becomes + 4.
If the blank starts as - ( ), flip both sides one more time.

Practice Problems

Score: 0 correct out of 0 tries

Only + and -, one blank, and kid-sized numbers.