Joyce baked a cake using 2 3/4 cups of brown sugar and 1 3/4 cups of powdered sugar. how many cups of sugar did she use in her cake? (answers above in photo)

So she has used two kinds of sugar, brown and powdered.

She used cups of brown sugar and  cups of powdered sugar: we need to add the two numbers:

+= 2+1+=3

so the correct answer is 4.5

Hope i can you!