Hey!
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Ratios can be written as a fraction or something like a:b
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The ratio between crayons to erasers:
24:2 or 24/2 (For every 12 crayons there will be 1 eraser)
The ratio between total items to pens:
5 + 2 + 3 + 12 + 24 = 45
45:3 or 45/3 (For every 15 items there will be 1 pen)
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Hope This Helped! Good Luck!