Answer:
14 years 7 months
Step-by-step explanation:
If the average age was increased by 2 months by adding a 7th child, the total age was increased by 2·7 months = 14 months more than the previous average. That is, the added child's age is 14 months more than the previous average, so is ...
... (13 years + 5 months) + (1 year + 2 months) = 14 years + 7 months
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For the non-believers:
The previous total of all ages was ...
... 6 × (13 years 5 months) = 80 years 6 months
The new total of all ages is ...
... 7 × (13 years 7 months) = 95 years 1 month
The amount added to the previous total is ...
... (95 1/12 - 80 6/12) years = 14 7/12 years = 14 years 7 months
