Answer:
Let's assume that the original price of petrol is x per liter.
After the increase of R1 per liter, the new price of petrol is (x+1) per liter.
According to the problem, with the new price, you can buy 7 liters less for R504, so we can write:
7(x+1) = 504
Simplifying this equation, we get:
7x + 7 = 504
Subtracting 7 from both sides, we get:
7x = 497
Dividing both sides by 7, we get:
x = 71
Therefore, the original price of petrol was Rx71 per liter.