Distance reading at the start of journey = 12468
Distance reading at the end of the journey = 12845
Distance traveled in the journey = 12845 - 12468 = 377 miles
Cost of petrol per mile = 13p
Cost of petrol for the journey = 13 × 377 = 4901p
Since one pound is one hundred pence, 4901p in pounds will be 4901/100 = 49.01 pounds
Cost of petrol used in the journey is 49.01 pounds