Answer:
1022 minutes
Step-by-step explanation:
Let x be the number of minutes the executive used the phone
There is a base charge of $35 and only minutes greater than 900 min are charged at the rate of $0.40 per minute
So total bill A = 35 + 0.4(x-900)
We know the bill was $83.80
So we can rewrite the equation as
35 + 0.4(x-900) = 83.30
and solve for x
To make it easier for computational purposes
1) Multiply both sides by 10
[tex]35\cdot \:10+0.4\left(x-900\right)\cdot \:10=83.8\cdot \:10[/tex]
2) Perform individual multiplication
[tex]350+4\left(x-900\right)=838[/tex]
3) Subtract 350 from both sides
[tex]350+4\left(x-900\right)-350=838-350[/tex]
4) Simplify
[tex]4\left(x-900\right)=488[/tex]
5) Divide both sides by 4
[tex]\frac{4\left(x-900\right)}{4}=\frac{488}{4}[/tex]
6) Simplify
[tex]x-900=122[/tex]
7) Add 900 to both sides to isolate x
[tex]x-900+900=122+900[/tex]
8) Simplify to obtain x
[tex]x=1022[/tex]
Answer: The executive used the phone for 1022 minutes that month
