Question 1065336

  J = Jane's age
  K = Joy's age
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   J = 2K   (1)
  J+4 = (K+4)+10   (2)
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Substitute 2K for J (from (1)) into (2): 
   2K+4 = K+4+10
         K = 10  —>  from (1): J = 2K = 20
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Ans:
 Joy is 10,  Jane is 20
——
Check:
               Joy's age in 4 years:   10+4 = 14
               Jane's age in 4 years:   20+4 = 24 = 14+10  (ok, 10 more than Joy's)