To solve for x, we must first isolate the term containing x which in this problem is 5x.
Since 10 is being added to 5x, we subtract 10 from both sides of the equation to isolate the 5x.
On the left, the +10 and -10 cancel out and on the right, 20 - 10 is 10 and we have 5x = 10.
Now we can finish things off by just dividing both sides of the equation by 5. On the left the 5's cancel and on the right, 10 divided by 5 is 2 so x = 2.
