Question: $50 upfront charge and 0.20cents per km
A) cost equation for kilometres traveled(d)
B) $120 is the cost, what is the distance traveled
Let $\displaystyle C$ = Total cost
Let $\displaystyle d$ = Distance traveled
They charge to $50.00 plus $0.20 every km.
So,
$\displaystyle C=0.20d+50$
If the total cost is $120.00
Then
Let $\displaystyle C=120$
Substitute.
$\displaystyle 120=0.20d+50$
Solve for $\displaystyle d$
Subtract both sides with 50
$\displaystyle 120-50=0.20d+50-50$
$\displaystyle \Rightarrow$
$\displaystyle 70=0.20d$
Multiply both sides by 5 (to make 0.20=1)
$\displaystyle 70*5=0.20d*5$
$\displaystyle \Rightarrow$
$\displaystyle 350=d$