PHP Data Types

Numbers: Integers and Floating-Point (Decimal)

QUESTION: Don't need quotes or single quotes for these numbers within variable...Unless a break is added within the PHP?

QUESTION: you can place "
(Shift + Return) within a PHP line to break; but apparently, this means that line must become a string, with quotes? And sometimes it don't work right; you end up not with the sum, but with the 'literals', the two assigned numbers, with "+" between them. What is going wrong here?

Math

QUESTION: in this last calculation, the code was temperamental; I had to re-enter it several times to get it to work. Why?