Subtract from a 2-digit number crossing the tens (no help)
Subtract a single digit from a 2-digit number up to 20.
Subtract from a 2-digit number crossing the tens (no help)
Subtract a single digit from a 2-digit number up to 20.
Subtract a single digit from a 2-digit number up to 20.
Subtract a single digit from a 2-digit number up to 20.