Answer
The mean is a bit more than 44.1 but still quite close.
Work Step by Step
The mean can be counted by summing all the data and dividing it by the number of data. Also, at each age group we take the mid range of the group to calculate. The mid ranges: 20-29:24.5, 30-39:34.5, 40-49:44.5, 50-59:54.5, 60-69:64.5, 70-79:74.5. The mean: $\frac{24.5\cdot1+34.5\cdot26+44.5\cdot35+54.5\cdot13+64.5\cdot6+74.5\cdot1}{82}=44.5$. The mean is a bit more than 44.1 but still quite close.