1) Read the question. Understand the problem. What are you answering? What unit are you answering in? $, Km.....
2)Make a plan. Draw the problem. Make a chart. Try a smaller case.
3) Carry out the plan. Check each step.
4) Look back. Think about your answers. Are they reasonable? Have you answered the question?
Problem: You have a 3 liter jug and a 5 liter jug and an unlimited supply of water. Can you measure 4 liters?
Fill the 3-liter bottle and pour it into the empty 5-liter bottle.
Fill the 3-liter bottle again, and pour enough to fill 5-liter bottle.
This leaves exactly 1 liter in the 3-liter bottle.
Empty the 5-liter bottle; pour the remaining 1 liter from the 3-liter
bottle into the 5-liter bottle.
Fill the 3-liter bottle and pour it into the 5-liter bottle. The
5-liter bottle now has exactly 4 liters.
If you got the answer right - congratulations!