Answer:
you find the sum by adding a "0" at the end of "4.2" and the stack add them (or however you can add them).
Step-by-step explanation:
4.20
+ 2.14
= 6.34
U^2(2u+3)+7(2u+3)
(u^2+7)(2u+3)
So if we take 1/4 to be the 100%, what is 2/3 in percentage off of it then?

yes, is a large value, because 2/3 is indeed larger than 1/4, more than twice as large.