twice a number plus 4 is 8

Let's take the number as 'x'
Twice : 2x
Plus 4 : 2x + 4
This is equal to 8.
... 2x + 4 = 8
Subtracting 4 on both sides :
... 2x = 4
Dividing by 2 on both sides :
... x = 4 / 2
... x = 2
Hence, the number is 2.
Hope this helps!