Let the fixed charge be ‘a’ and the charge per km travelled be ‘b’
Given,
For a journey of 12 km, the charge paid is Rs 89 and for a journey of 20 km, the charge paid is Rs 145
⇒ a + 12b = 89 ----- (1)
and a + 20b = 145 ----- (2)
(1) – (2)
⇒ - 8b = - 56
⇒ b = 7
Thus,
a + 84 = 89
⇒ a = 5
For a distance of 30 km,
amount paid = distance travelled x charge per kilometre + fixed charge
= 30 × 7 + 5 = Rs. 215