contestada

Sebastian was in a hotel lobby and took the elevator up 7 floors to his room. Then he took the elevator down 9 floors to the parking garage. He described his movement with the expression below. 9 + (–7) What is Sebastian’s error?

a.Sebastian should have used –9 and 7.
b.Sebastian should have started at zero before adding –7.
c.Sebastian should have switched the two addends and written –7 + 9.
d.Sebastian should have used 0 and –9.