multiply 20 by 5 and you get 100, please tell if this is what you wanted!
The fist box would be 40 and the second box would be 10. If you change 4/10 to have the same denominator as 100 it is 40 over 100. and if you say 8 is over 10 then it is 80 / 100. And 80 - 40 = 40, so it is 40.
