Final answer:
Mr. Christianson has 44.3 pounds of mulch left over.
Step-by-step explanation:
To find out how much mulch Mr. Christianson has left, we need to subtract the amount he needed from the amount he ordered.
Subtracting 43.7 pounds from 88 pounds, we get:
88 pounds - 43.7 pounds = 44.3 pounds
Therefore, Mr. Christianson has 44.3 pounds of mulch left over.