Tod had 3/4 of an apple left from breakfast his sister ate 1/8 of what was left. how much of the apple is left

You have to change 3/4 to 6/8 by multiplying the numerator and denominator by 2.
Now you can add 6/8 and 1/8, to get 7/8. 8/8 - 7/8 is 1/8
1/8 of the apple is left.

This does not make sense