Ireally don't get how to do them and i am in a rush some

I will try to some of the different types of the problems presented and then leave the rest for you to do. Just remember that if you know how to do one of them, then the others should be of no problem to you.

5x + 8 = 23
To solve for x, we need to make sure that it is isolated (or by itself). So we can subtract 8 from both sides of the equation (the opposite operation of addition is subtraction).
5x + 8 - 8 = 23 - 8
5x = 15
Now divide both sides by 5 (the opposite operation of multiplication is division). 
5x / 5 = 15 / 5 
x = 3 

Another one I will do is 
Just like the previous problem that I have done, you need to add 4 to both sides because addition is the opposite operation of subtraction.
(s / 3) - 4 + 4 = 2 + 4
(s / 3) = 6
 Since s is being divided by 3, we need to multiply both sides by 3 because the opposite of division is multiplication.
(s / 3) x 3 = 6 x 3
s = 18