Subtraction takes one amount away from another. If you have
a things and remove b
of them, you have:
a - b = c
One way to picture it is to start at a on a
number line and take b steps to the left —
this is called counting back. Press play, then replay it: each
time it starts at a new random number and takes a different amount away,
reading each number aloud as it hops. The dots still standing at the end
are the answer.
Khan Academy walks through basic subtraction here: