So, we want to get the variable by itself on one side. We do this by doing the opposite operation, starting with terms that don't include the variable. We have to remember to do the same thing to both sides of the equation.
For example, 6 + 1 = 7, right? If I subtract 1 from both sides, I get 6 + 1 - 1 = 7 - 1, so 6 = 6. Hey, that's true! If I only subtract 1 from the left side, a common error, I end up with 6 = 7, which is not true.
So....
5x + 3 ≤ -7
Well, we subtract 3.
5x + 3 - 3 ≤ -7 - 3
5x ≤ -10
Since 5x = five times x, we divide by 5. 5/5 = 1, but we don't write 1x.
5x/5 ≤ -10/5
x ≤ -2
What does that look like on a number line? Because -2 is included, we have a dot on -2 with an arrow pointed left.
