A car travels 240 km on 20 liters of petrol. how many litres of petrol is needed to travel 600 km

If 1/√5+1/√5+1=p+q√r , find the values of p, q and r

The zoo collects $9.60 for every 24 tickets sold. how much will be collected for 400 tickets?

I'm at a bookstore with $\$35$ in my pocket and a $20\%$-off coupon. what is the cost of the most expensive book i can buy with my money and the coupon? (assume that there are books of every possible price in the bookstore. it's a large bookstore! )