28a^11b^7/4a^3b

If your expression mean :

( 28 a ^ 11 b ^ 7 ) / ( 4 a ^ 3 b ) then :

( 28 a ^ 11 b ^ 7 ) / ( 4 a ^ 3 b ) =

( 28 / 4 ) * ( a ^ 11 / a ^ 3 ) * ( b ^ 7 / b ) =

7 a ^ 8 b ^ 6