Answer:
least = 13 tons
greatest = 23 tons
Reason
The smallest an elephant can weigh is 4.4 tons.
Three such elephants weigh at minimum 3*4.4 = 13.2 tons. This rounds to 13 tons.
Also, three elephants weigh at most 3*7.7 = 23.1 tons. That rounds to 23 tons.
The span of weights is from 13 tons to 23 tons, when rounding to the nearest ton.