Hello I've received holiday homework from my text book and i cant seem to work ou these questions. anyone know the working outs?i saw the answer from the back of the book but i don't just want to copy it i want to understand it

thanks.:]

1)Two tanks contain equal amounts of water. They are connected by a pipe and 3000 litres of water is pumped from one tank to the other. One tank then contains 6 times as much water as the toher. How many litres of water did each tank contain originally.

Answer:4200L

2)a boy is 24 years younger than his father. In 2 years time the sum of thier ages will be 40. find the present ages of father and son.

Answer: father-30 son-6

3)A man travels from A to B at 4km/h and from B to A at 6km/h. the total journey takes 45 minutes. find the distance traveled

answer- 3.6km

4) jess walked for 45 minutes at 3km/h and then ran for half an hour at xkm/h. At the end of that time she was 6km from the starting point. find the value of x.