Lucca has 100 basketballs x (10 / 100) = <<100*10/100=10>>10 basketballs.
Lucien has 200 basketballs x (20 / 100) = <<200*(20/100)=40>>40 basketballs
Together they have 10 basketballs + 40 basketballs = <<10+40=50>>50 basketballs.
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