ExplanationRather than assigning separate variables to the granddaughters and grandsons, define them both in terms of the same unknown multiplier, based on the ratio given:
Number of granddaughters = 3m
Number of grandsons = m
Note that you are solving for 3m, not for m!
3m + m = 12
4m = 12
m = 3
3m = 9
Alternatively, suppose that Nash had exactly one grandson and three granddaughters.
That would sum to four grandchildren altogether. Triple the number of grandsons and granddaughters to triple the number of grandchildren.
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