I am not 100% sure this is right but I believe its 28:)
Answer:
Sylvia needs 12 l of orange juice and 9 l of pineapple juice.
Step-by-step explanation:
triple means multiplying by 3
so multiply 4 l of orange juice by 3 and 3 l of pineapple juice by 3
1.5, 2.25, 3.375, 5.0625, 7.59375... and so on
.6 divided by 10 is .06 so .6 is 10 times more than .06