Question 1203623
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Jack is 7 years older than Mia. The sum of {{{highlight(cross(there))}}} <U>their</U> ages is 53. How old is Jack.
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Again, it is nice problem to solve it MENTALLY in 6 seconds, without using equations.


Indeed, consider/imagine another person Jack' instead of Jack, who (Jack') is 7 years younger than Jack.


Then Jack' and Mia both are of the same age, and the sum of their ages is 53-7 = 46.


Hence, Jack' is 46/2 = 23 years old.


It implies that Jack, the true person, is 23 + 7 = 30 years old.



At this point, the solution is complete.