This works a lot like addition...

Let's try

7/8 - 3/8

Look at a pizza cut into 8 pieces. Each piece 1/8 slice of pizza is of the pizza.

7/8=

1/8 slice of pizza1/8 slice of pizza1/8 slice of pizza1/8 slice of pizza1/8 slice of pizza1/8 slice of pizza1/8 slice of pizza

Take 3/8 away (that's 3 pieces):

1/8 slice of pizza1/8 slice of pizza1/8 slice of pizza1/8 slice of pizza1/8 slice of pizza crossed out1/8 slice of pizza crossed out1/8 slice of pizza crossed out

We're left with 4 pieces - that's .

So 7/8 - 3/8 = 4/8

But, look what we really did!

We just subtracted the numerators!

7/8 - 3/8 = (7-3)/8 = 4/8  which is  1/2