A jar contains 0.75 liter of blackberry juice and 0.60 liter of blueberry juice. Patrick poured 0.25 liter of guava juice into the jar. He then drank 0.20 liter of the mixture.
Part A: Write an expression to represent the total amount of juice left in the jar. (5 points)
Part B: Simplify the expression and identify which property is used in each step. (5 points)