21\(^{15}\) = ( 3.7 )\(^{15}\) = 3\(^{15}\).7\(^{15}\)
27\(^5\).49\(^8\)= ( 3\(^3\))\(^5\).(7\(^2\))\(^8\)= 3\(^{15}\).7\(^{16}\)
For 15 < 16 candle 7\(^{15}\)< 7\(^{16}\) = > 3\(^{15}\).7\(^{15}\)< 3\(^{15}\).7\(^{16}\)
Or 21\(^{15}\)< 27\(^5\).49\(^8\)