To calculate 5 of 50, you simply take 5 and find its proportion of 50. This is done by setting up the equation:
5/50 = 0.1
This means that 5 is 10% of 50. In other words, if you have a whole of 50 and you take away 5, you are removing 10% of that whole. If you want to calculate it another way, you can multiply 50 by 0.1, which also gives you 5.