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Answer:
49.3 feet
Step-by-step explanation:
Shadow lengths and object heights are considered to be proportional, so we have ...
tree height/(tree shadow) = Andrew's height/(Andrew's shadow)
height / (85 ft) = (5.8 ft)/(10 ft)
height = (85 ft)(5.8/10) = 49.3 ft
The tree is 49.3 feet tall.