Question 1171651
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Let x be the Rebecca's age.

Then Jack's age is  3x-5.


From the condition, you have this equation for the sum of ages

    x + (3x-5) = 75.


Simplify and solve

    x + 3x = 75 + 5

     4x    =    80

      x    =    80/4 = 20.


<U<>ANSWER</U>.  Rebecca is 20 years old.   Jack is 3*20-5 = 55 years old.
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Solved.