System of equations?
I need help setting up 3 equations...
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computerwarehouse.com charges $3 for shipping orders up to 10 lb, $5 for orders from 10 lb up to 15 lb, and $7.50 for orders of 15 lb or more. One day shipping
a = $3 b = $5 c = $7.5
3c = a
a+b+c= 150
3a + 5b + 7.5 c = 680