Jackson's age was 2/5 of the age he will be 20 years from now. How old is Jackson now?

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.