Question

Tara's cell phone plan costs $39.00 a month, which includes 100 text messages. After she uses all of her text messages, it will cost her $.15 per text message

Answer 1

i have to write an equation that could be used to determine the total cost of her cell phone bill after her first 100 messages.

Answer 2

@jim_thompson5910

Answer 3

let x = number of messages over 100 (eg: x = 3 means she sent 103 messages)


so if it costs $39 a month + $0.15 per message over 100 messages, then

cost = 39 + 0.15*(number of messages over 100)

y = 39 + 0.15x

where y is the cost and again x is the number of messages over 100

Answer 4

this equation is only valid if she sends over 100 messages

Answer 5

well y=39+.15x would be my equation then, the question asks me that if tara only wants to spend $43 how many txt messages can she send?

Answer 6

replace y with 43 (since y is the cost)

Answer 7

to get

y=39+.15x

43=39+.15x

Answer 8

now solve for x

Answer 9

well i subtracted 39 on both sides and got 4=.15x

Answer 10

good

Answer 11

then what

Answer 12

well i would divide 4 by .15 but it comes out a decimal so then what?

Answer 13

4/0.15 = 26.667

so x = 26.667

you then round down to get x = 26

Answer 14

oh alright

Answer 15

you round down because if you rounded up, your final bill would be over $43