First, I think it would be easier to put it in decimal form
4/5 cup of tomato paste is 0.8 cup
1 1/4 cup of water is 1.25 cups
using cross multiplication,
0.8 cup of tomato paste
over
1.25 cups of water
is equal to
x cups of tomato paste
over
3 cups of water
0.8 × 3 = 2.4
1.25 × x = 1.25x
2.4 = 1.25x
1.92 cups of tomato paste = x
