21 1/2m - 7 3/10m - 6 3/8

[tex]21 \frac{1}{2} - 7 \frac{3}{10} - 6 \frac{3}{8} \\ = \frac{43}{2} - \frac{73}{10} - \frac{51}{8} \\ = ( \frac{43}{2} ) \times 20 - ( \frac{73}{10} ) \times 4 - ( \frac{51}{8} ) \times 5 \\ = \frac{860 - 292 - 255}{40} \\ = \frac{313}{40} \\ = 7 \frac{33}{40} [/tex]
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