You can
put this solution on YOUR website!well, use a calculator?
if you need to do it by hand, then... 4.242x10^2 is 424.2
So
424.2/2.1 is 202 so we have

which can be thought of as

which then becomes

which is 2020.
This is a fair bit of messing around with numbers, but is all good practice for you.
jon.