A walking person was able to cover a distance of 3 kilometers in 15 minutes. What is the speed of the person? 

What is the complement of $40°$ ?

How many liters of 30% alcohol solution should be added to 20 liters of a 50% alcohol solution to make a 40% solution?

 A train covers a distance of 90 kilometers. If its speed becomes 15 kph more it would take 30 minutes less for the whole trip. What is the ideal speed of the train? 

What is the complement of $70°$

The sum of a positive number and its square is equal to 6. What is the number?

Ana went to a party, which is 120 kilometers from her home. On her way home, she drove 10km/hr slower because of a road construction which took her 2 hours longer. How fast did she drive on her way home from the party?

Ana went to a party, which is 120 kilometers from her home. On her way home, she drove 10km/hr slower because of a road construction which took her 2 hours longer. How fast did she drive on her way to the party?

A bus and a car covered a distance of 60 kilometers. The speed of the bus is 10 km faster than the car and arrived 2 hours earlier. What is the speed of the car?

How many liters of 40% alcohol solution should be added to 30 liters of a 50% alcohol solution to make a 45% solution?