Answer:
14 units
Step-by-step explanation:
All we have to pay attention to in this problem is B, so we can ignore the rest of the triangle. B is 5 units directly to the left of line l, meaning that B' must be 5 units to the right of line l. This would put B' 2 units to the left of line m. That means that B" would be 2 unit to the right of line m, as that is how reflections work. Adding up all of the difference in units you have a 10 unit shift from B to B', and then a 4 unit shift from B' to B". Now adding 4+10=14 units.
