Answer 1

x = x + 1 can be written in another way like x += 1.

x = x * 5 can be written as x *= 5
Just a short form but does the same task.

Answer 2

When u use =, u are assigning a value to a variable.
x = 10
Now x is 10.
If u now say,
x = x + 5
Now x is 15, because 10 + 5.
x = x * 2
Now x is 30, because 15 * 2.

Answer 3

Rik no problem :)