6. Mr Chua's car consumes petrol at an average rate
of 8 litres daily. Before Mr Chua begins his journey,
he tops up the petrol in his car to 100 litres. Given
that he will next top up the petrol in his car when
there are 20 litres left, form an inequality and solve
it to find the maximum number of days he can travel
before he has to top up the petrol in his car. 10