Answer:
[tex]y=18x+45[/tex]
Step-by-step explanation:
we know that
The linear equation in slope intercept form is equal to
[tex]y=mx+b[/tex]
where
m is the slope or unit rate of the linear equation
b is the y-intercept or initial value of the linear equation
Let
x -----> the number of months
y ----> total charges in dollars
In this problem
The slope or unit rate is equal to
[tex]m=\$18\ per\ month[/tex]
we have the ordered pair (2,81)
substitute in the equation
[tex]81=(18)(2)+b[/tex]
solve for b
[tex]81=36+b[/tex]
subtract 36 both sides
[tex]b=81-36=\$45[/tex] -----> initial set up fee
therefore
The equation is
[tex]y=18x+45[/tex]
