Question

Refer to the attachment.
do it in copy if you wanna. .
$a = \frac{ - 11}{27}$
$b = \frac{4}{9}$
$c = \frac{ - 5}{8}$

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Answer 1

$\sf \: a + (b+ c) = (a + b) + c$

$\sf \:\frac{ - 11}{27} +( \frac{4}{9} + \frac{ - 5}{8} ) =(\frac{ - 11}{27} + \frac{4}{9}) + \frac{ - 5}{8}$

$\frac{ - 11}{27} + ( \frac{ 32 - 45}{72} ) = \frac{ - 99 + 108}{243} - \frac{ 5}{8}$

$\frac{ - 11}{27} - \frac{13}{72} = \frac{ 9}{243} - \frac{5}{8}$

$\frac{ - 792 - 351}{1944} = \frac{ 72 - 1215}{1944}$

$\frac{1143}{1944} = \frac{1143}{1944}$

$\frak{1 = 1 \: (proved)}$