Question

$\\ verify\\ \\ x = \frac{3}{4} \: \: y = \frac{5}{6} \: \: z = \frac{ - 7}{8}$
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Answer 1

x = (y + z) = (x + y) + z \\ \\ x = (y + z) = \frac{3}{4} + ( \frac{5}{6} + \frac{ - 7}{8} ) \\ \\ = \frac{3}{4} + ( \frac{20 + ( - 21)}{24} ) \\ \\ = \frac{3}{4} + ( \frac{ - 1}{24} ) \\ \\ = \frac{3}{4} + \frac{ - 1}{24} \\ \\ = \frac{18 + ( - 1)}{24} \\ \\ = \frac{17}{24} \\ \\ (x + y ) + z = ( \frac{3}{4} + \frac{5}{6} ) + \frac{ - 7}{8} \\ \\ = ( \frac{9 + 10}{12} ) + \frac{ - 7}{8} \\ \\ = \frac{19}{12} + \frac{ - 7}{8} \\ \\ = \frac{38 + ( - 21)}{24} \\ \\ = \frac{38 - 21}{24} \\ \\ = \frac{17}{24} \\ \\ x + (y + z) = (x + y) + z \\ \\

Verified

Answer 2

$x = (y + z) = (x + y) + z \\ \\ x = (y + z) = \frac{3}{4} + ( \frac{5}{6} + \frac{ - 7}{8} ) \\ \\ = \frac{3}{4} + ( \frac{20 + ( - 21)}{24} ) \\ \\ = \frac{3}{4} + ( \frac{ - 1}{24} ) \\ \\ = \frac{3}{4} + \frac{ - 1}{24} \\ \\ = \frac{18 + ( - 1)}{24} \\ \\ = \frac{17}{24} \\ \\ (x + y ) + z = ( \frac{3}{4} + \frac{5}{6} ) + \frac{ - 7}{8} \\ \\ = ( \frac{9 + 10}{12} ) + \frac{ - 7}{8} \\ \\ = \frac{19}{12} + \frac{ - 7}{8} \\ \\ = \frac{38 + ( - 21)}{24} \\ \\ = \frac{38 - 21}{24} \\ \\ = \frac{17}{24} \\ \\ x + (y + z) = (x + y) + z$