pineapple juice : orange juice : lime juice = 2:7:3
So there is 2x of pineapple juice, 7x of orange juice and 3x of lime juice.
[tex]2x+7x+3x=600 \\
12x=600 \\
x=50 \\ \\
pineapple \ juice \to 2x = 2 \times 50=100[/tex]
She used 100 ml of pineapple juice.