so we have 20 liters bought with the old price (a) and 10 liters with the new price (a + 2). This is translated into this equation where a is the old price therefore our quest to be answered
20 xa + 10 x (a + 2) = 920 (cents)
20 xa + 10 xa + 20 = 920
30 xa + 20 = 920
30 xa = 920 - 20
30 xa = 900
a = 900: 30
a = 30 (cents)
therefore the old price for 1 liter of petrol is 30 cents
(hope this helps can i plz have brainlist :D hehe)
