Balsamic Vinegar Ratio Problem

In a cooking class, Mia is making a special sauce that requires 3/4 cup of olive oil and 2/3 cup of balsamic vinegar. After checking her ingredients, she realizes she only has 1/2 cup of olive oil left in the bottle. If she uses all the olive oil she has, how much more balsamic vinegar does she need to maintain the ratio of olive oil to balsamic vinegar required for the sauce?