CAT 2017 [slot 1] Question with solution 24

$\frac{81^x}{9} - \frac{81^x}{81} = 1944$

$81^x × [\frac{1}{9}- \frac{1}{81}] = 1944$

$81^x × [\frac{8}{81}] = 243$

$3^{4x} = 3^9$

$x = \frac{9}{4}$