We know that he earns 420 every day. So if we want to know how much he earns over 5 days for example, we would multiply 5 and 420...
5 X 420= 2,100
We would do the same thing no matter how many days he works.
* remember that in an algebraic expression having a variable and a constant next to each other indicates that they are being multiplied.
So we can write that as
Money earned= 420d