Answer :
first find the difference so:
85 - 80 = 5
now find what percentage of 80 is 5
5/80 = 0.0625
so 6.25% or in your case 6.3%
85 - 80 = 5
now find what percentage of 80 is 5
5/80 = 0.0625
so 6.25% or in your case 6.3%