Question 320793
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Your question is grammatically incorrect.  It should read, "Mary is 20 and Betty is 53. At what age <i>was</i> Betty when she <i>was</i> three times older than Mary?"


Let *[tex \Large x] represent the number of years that have elapsed since the time Betty was three times older than Mary.


*[tex \LARGE \ \ \ \ \ \ \ \ \ \ 53\ +\ x\ =\ 3(20\ +\ x)]


*[tex \LARGE \ \ \ \ \ \ \ \ \ \ 53\ +\ x\ =\ 60\ +\ 3x]


*[tex \LARGE \ \ \ \ \ \ \ \ \ \ -2x\ =\ 7]


*[tex \LARGE \ \ \ \ \ \ \ \ \ \ x\ =\ -\frac{7}{2}]


*[tex \LARGE \ \ \ \ \ \ \ \ \ \ 53\ -\ \frac{7}{2}\ =\ 49.5]


Check:


*[tex \LARGE \ \ \ \ \ \ \ \ \ \ 3\left(20\ -\ \frac{7}{2}\right)\ =\ 3\ \times\ 16.5\ =\ 49.5]


John
*[tex \LARGE e^{i\pi} + 1 = 0]
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