Question

Evaluate:

viii) $-\frac{5}{7}-(-\frac{3}{8})$

Answer 1

Step 1: Finding LCM of denominators of
given numbers
Given, numbers $-\frac{5}{7},(-\frac{3}{8})$
$\therefore \text{LCM of}7,8$
$=2\times 2\times 2\times 7=56$.

Step 2: Making the denominators equal
to LCM and finding the result
Given: $-\frac{5}{7}-(-\frac{3}{8})$
$=-\frac{5\times 8}{7\times 8}-(-\frac{3\times 7}{8\times 7})[\because \text{LCM of}7,8=56]$
$=-\frac{40}{56}+\frac{21}{56}=\frac{-40+21}{56}=\frac{-19}{56}$

Hence, the required result is $\frac{-19}{56}$.