30 x 2/5 = <<30*2/5=12>>12 members ordered lemon juice.
So, 30 - 12 = <<30-12=18>>18 members did not order lemon juice.
Since 1/3 of the remaining ordered mango juice, then 18 x 2/3 = <<18*2/3=12>>12 members ordered mango juice.
Therefore, 18 - 12 = <<18-12=6>>6 members ordered orange juice.
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