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The answers are here.
Put the digits 1-3 (later 1-4 and 1-5) once each in the white circles and once each in the shaded circles. When 3 circles are adjacent in a straight line, the middle circle should contain the difference of the numbers in the other two circles. Some of the circles are already filled for you.
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O.
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Q.
R.
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The answers are here.