What is the likelihood the next crayon randomly selected will be yellow

So there are 10 crayons and 8 are yellow.  

This means that 8/10 of the crayons are yellow.  

So the chance of picking a yellow one is 80%.  

To get this, you need to do 8/10 and make it over 100, which is 80/100.  Then, you turn this number into a percent by just dropping the 100 and adding a % to 80 (it's this easy if the bottom denominator is 100) 

The work should look something like this;

8:10
8/10
80/100
80%

So, there is an 80% chance that the crayon you pick will be yellow.  Any questions?