Respuesta :

altavistard
Let j represent Jack's age now.  Then:

j = (2/5)(j+20)

Remove the fraction by mult. both sides by 5:

5j = 2(j+20), or 5j = 2j + 40.  Solving for j:  3j = 40.  Then j = 40/3, or 13 1/3 years.

Must check this result:      Is     j = (2/5)(j+20)  true when j = 40/3 years?


Is 40/3 = (2/5)(40/3+20)  true?

LCD is 15.  Then (40/3)(15) = (15)(2/5)(40/3 + 60/3), or

200 = 6(100/3).  Is this true?       Is 200 = 2(100) true?  YES.

Jack is 40/3 years old now, or 13 1/3 years.

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