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Two numbers differ by 9
Let x and (x+9) represent the smaller and larger respectively
Question States***
 4/7(x+9) = (3/4)x  + 3
solving for x
 16(x+9) = 21x +  84  Multiplying both sides of equation by 28
  144 + 16x = 21x + 84
     60 = 5x
      x = 12, the smaller number. Larger number is 21
CHECKING our Answer***
 4/7*21 = 12 = 3/4*12 + 3 = 9 + 3 = 12