AI Tutor
Imagine you have 16 sweet strawberries in a bowl, and a sneaky squirrel grabs 2. How can you find out how many are left without counting all the way from 1?
You can simply count backward! When you subtract 1, 2, or 3, just start at your big number and hop back like a frog.
What does this look like when we jump on a real number line?

Hopping Back on a Number Line

Let's solve 17−217 - 2. Find 17 on the line, then take 2 hops to the left: 16... 15!
Watch out for a tricky mistake: do not count 17 as your first hop! You only say 16 after your finger actually moves one step back.
What happens if we look at our numbers inside ten-frames instead?

Taking Away from Ten-Frames

A teen number is made of one full group of 10 and some loose ones. When you take away 1, 2, or 3, your full ten stays safe—you just cross out dots from the ones frame!
Let's try one more together: what is 19−319 - 3?