The total ratio representing the number of marbles is 3+5 +7 = <<3+5+7=15>>15

From the ratio, the fraction representing the number of marbles that Brittany has is 3/15, which is equal to 3/15*600 = <<3/15*600=120>>120 marbles.

Alex has 5/15*600 = <<5/15*600=200>>200 marbles.

If Brittany gives half of her marbles to Alex, Alex receives 1/2*120 = 60 marbles.

After receiving 60 marbles from Brittany, Alex has 200+60 = <<200+60=260>>260 marbles.

# Answer

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<|im_start|>system
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<|im_start|>user
Brittany, Alex, and Jamy all share 600 marbles divided between them in the ratio 3:5:7. If Brittany gives Alex half of her marbles, what's the total number of marbles that Alex has?
Please reason step by step, and put your final answer within \boxed{{}}.<|im_end|>
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user
260
Brittany, Alex, and Jamy all share 600 marbles divided between them in the ratio 3:5:7. If Brittany gives Alex half of her marbles, what's the total number of marbles that Alex has?
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