In this case, you don't want the numbers to be mixed up with variables. You also don't want to write the number on left and variable on the right. We keep variable on the left and number on right. We need to get rid of -3.8. To do so, add 3.8 on both sides. Adding 3.8 will be the first step.
Part 1 is ELevator 2 because elevator one ends on floor 9 and elevator 2 ends on floor 23. Part 2 is Elevator 1 ends on floor 9 and Elevator 2 ends on floor 23.
