Step 1) Identify what you are asked to calculate.
Step 2) What info would you need to be able to use that formula.
Step 3) Are you given the info directly or do you need to do some calculations first?
In this example we would use the Pythagorean Theory.
Step 1) Identify what you are asked to calculate which in this case would be (x).
Step 2) We would need atleast two sides to use the formula, which are 10 m and 4 m. Step 3) We must make some calculations to find the value of (x).