We develop the ratio between the number of milliliters present in 1 tablespoon and that is, 15 mL: 1 tablespoon We let x be the number of millileter in 3 tbsp and it can be determined through the equation below. x = 3 tbsp x (15 mL/ 1 tbsp) = 45 mL Therefore, there are 45 mL in 3 tbsp.