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5a = 50 + a.
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d2 = d*10 + 10 = 10d + 10.
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m4m = m*100 + 40 + m = 101m + 40.
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86k = 8*100 + 6*10 + k = 860 + k.
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mn1 = m*100 + n*10 + 1 = 100m + 10n + 1.
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16b = 1*100 + 6*10 + b = 160 + b.
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9abc = 9*1000 + a*100 + b*10 + c = 9000 + 100a + 10b + c.
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mnkl = m*1000 + n*100 + k*10 + l = 1000m + 100n + 10k + l