On the first day, Cleo and Ignacio took 3/5 * 30 marbles = <<3/5*30=18>>18 marbles from the jar

When they shared the marbles, each got 18 marbles / 2 people = <<18/2=9>>9 marbles/person

The total number of marbles remaining in the jar is 30 marbles - 18 marbles = <<30-18=12>>12 marbles

On the third day, Cleo took 1/2 * 12 marbles = <<1/2*12=6>>6 marbles from the jar.

The total number of marbles she has on the third day is 6 marbles + 9 marbles = <<6+9=15>>15 marbles.

# Answer

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Cleo and Ignacio placed 30 of their marbles in a jar on a Monday. They took 3/5 of the marbles from the jar the next day and divided them equally. On the third day, Cleo took 1/2 of the marbles remaining in the jars. How many marbles did Cleo have on the third day?
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Cleo and Ignacio placed 30 of their marbles in a jar on a Monday. They took 3/5 of the marbles from the jar the next day and divided them equally. On the third day, Cleo took 1/2 of the marbles remaining in the jars. How many marbles did Cleo have on the third day?
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