Question

What is 3/4 of a 2 liter bottle in millimeters

Answer 1

I believe you meant milliliters.  If so the answer is 1500ml

2 liters = 2000ml

2000/4 = 500 for 1/4

We need 3/4 so we multiply 500 X 3 and get 1500ml

Answer 2

If there are 1000 mL in one L we have 1000 plus half is 500 and half of that is 250 which means that 3/4 is 750 add to get 1750 mL