Lydia brought 4 liters of lemonade to a picnic. She poured 160 millimeters of lemonade for each of her 2 friends and 215 millimeters for another friend. How much lemonade does Lydia have left

1 litre=1000mL so we know that 4x1000 = 4000mL

Since she poured 160 mL for TWO friends

160x2=320

She then says that another friend has 215 mL of lemonade.

So that means

4000-320-215 = 3465 mL

Therefore Lydia has 3465mL or 3.465L of lemonade left