Tick (✓) the correct answer

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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