Let fixed charge =Rs.x and charge per kilometer =Rs.y
According to the question, x+12y=45…(i)
and x+20y=73… (ii)
On subtracting Eq. (i) from Eq. (ii), we get
x+20y−x−12y=73−45
⇒8y=28
⇒y=288=3.5
On putting the value of y=3.5 in Eq. (i), we get
x+12(3⋅5)=45⇒x+42=45
⇒x=45−42=3
Hence, monthly fixed charges is Rs. 3 and charge per kilometer is Rs. 3⋅5