Here I'll help you:
In order to solve the problem we must take the "x" to one side, and the numbers to the other side. When we move the three to the other side of the equation, we must change the "negative" to a positive [if it were to be positive, we'd make it negative.]
Now we have: 5 + 3 = 15x
Let's solve the left side.
We'll have: 8 = 15x
Now we have to divide both sides by 15.
Our answer would be:
.5333333 = 1x
In short, your answer is: X = 5.333333