If your question is how many positions are possible, then the answer is 24.
We find this by thinking of how many people can be in each spot. If there are 4 spots each person can stand (back left, back right, front left, front right), then there are 4 possible choice for the first spot (mom, dad, son, daughter), then 3 for the next spot (since 1 is already in a spot), then 2 options for the next spot, and then 1 option for the last spot. In other words, the answer is 4x3x2x1, or 4 factorial.
First you make the mixed numbers/fractions into improper fractions. After that, you must find the common denominator, the LCM of 9 and 6 (for the 2nd problem). After that, if you can, simplify the fraction to lowest terms, which also includes making it a mixed number/fraction.
I hope this helps! :)
Answer:
15 and 5 hours.
Step-by-step explanation:
Call x the time taken by the first chap, and y the second.
Let's divide by 5 and play with the LHS of the first equation a bit:
we know how much x+y is ( first equation!) let's solve.
At this point it's easy to check that 
Step 1: Write down the decimal<span> divided by 1, like this: </span>decimal<span> 1. Step 2: Multiply both top and bottom by 10 for every number after the </span>decimal<span> point. (For example, if there are two numbers after the </span>decimal<span> point, then use 100, if there are three then use 1000, etc.) Step 3: Simplify (or reduce) the </span>fraction<span>.</span>
