Question

a basic cellular phone plan costs $18 per month for 50 calling minutes. Additional time costs $0.30 per minute. The formula C = 18+0.30 (x-50) gives the monthly cost for this plan for calling minutes, where x > 50. How many calling minutes are possible for a monthly cost of minimum $30 and a maximum $45?

Answer 1

30 <= 18+0.3(x-50) <= 45
12 <= .3(x-50) <= 27
40 <= x-50 <= 90
90 <= x <= 140

Answer 2

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