Question

A recipe calls for 2 3/4 cups of flour . You already put in 1 1/4 .

Answer 1

So you would do...
2 3/4 - 1 1/4 = 1 2/4 which simplifies to 1 1/2

Answer 2

if you want to know how much you need left to put in the answer is: in bold

2 3/4 - 1 1/4 =
2 -1 = 1
and 3/4 - 1/4 = 2/4 which simplifies to 1/2

so your final answer is 1 1/2 cups of flour

hope this helps :)