Question:
Tick (✓) the correct answer
If $\frac{n}{2}-\frac{3 n}{4}+\frac{5 n}{6}=21$, then $n=$ ?
(a) 30
(b) 42
(c) 36
(d) 28
Solution:
(c) 36
$\frac{n}{2}-\frac{3 n}{4}+\frac{5 n}{6}=21$
$\Rightarrow \frac{6 n-9 n+10 n}{12}=21$
$\Rightarrow 7 n=21 \times 12$
$\Rightarrow 7 n=252$
$\Rightarrow n=\frac{252}{7}=36$
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