Three times the sum of marbles that Atticus, Jensen, and Cruz have is equal to 60, meaning together they have 60/3=<<60/3=20>>20 marbles.
If Atticus has half as many marbles as Jensen, and Atticus has four marbles, Jensen has 2*4=<<4*2=8>>8 marbles.
Together, Atticus and Jensen have 8+4=<<8+4=12>>12 marbles.
Since the sum of marbles that Atticus, Jensen, and Cruz have is equal to 20, and Atticus and Jensen have 12 marbles, Cruz has 20-12=<<20-12=8>>8 marbles.
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