STEP ONE: Add 4 to each side. You want to make sure to keep each variable to their own separate side!
13x - 4 < 12x - 1
13x < 12x + 3
STEP TWO: Subtract 12 from each side. Remember! You want each variable to be on their own separate sides! In this case, the x variable is on the left side and the numbers are on the right side.