Step-by-step explanation:
There are 5 different positions of 666:
666////
/666///
//666//
///666/
////666
The forward dashes represent any number from 0 to 9.
Case 1: "666////"
Number of ways = 10⁴ = 10,000.
Case 2: The other positions.
Since the 1st forward dash cannot be 0 (leading digit),
Number of ways for each position = 9 * 10³ = 9,000
Number of ways for all 4 positions = 9,000 * 4 = 36,000.
Total evil numbers = 10,000 + 36,000 = 46,000.
Example:
We can see that there is more than one number with the variable x, therefore, we say they're ''like terms'' and because of that they can be summed. We do this with all of the other numbers with similar variables. If no numbers with similar variables are left, like 4a, you don't do anything but write them as they are. You can also see that 8 and 9 can also be summed because neither of them has a variable, therefore they're similar.
In this step, you just do the operation with the numbers and keep the same variable.
since there are not more numbers similar in variables, this operation is done.
X is the number
sum means add
sum of half a number and 4 means
(x/2)+4
result is -16
(x/2)+4=-16
minus 4 both sides
x/2=-20
times 2 both sides
x=-40
the number is -40