a percent can always be turned into a decimal by moving the percent sign 2 spaces to the left like 15% would now be .15
this can also be reversed
a fraction can also be made into a decimal or percentage by getting it to its lowest factor such as 25/100 this can also be condensed down to 1/4 because 25 goes into 100 4 times evenly. Then 1/4 is 25% or .25
if you can condense the fraction to a decimal you can add, subtract and multiply them with ease.
when doing anything with a fraction jusf remember the common denomiator is the key. the bottom number on the fraction has to match so you can move forward with the problem.
1/4 + 1/8= 4 goes into 8, 2 times so it becomes
2/8+1/8=3/8
i hope this helps its the best way i know to describe how to do it