First, lets make these improper fractions
5*7=35+1=36/7
4*12=48+1=49/12
Second we must find a common denominator
7*12=84
49*7 = 343/84
36*12 = 432/84
(432-343)/84
89/84
Simplify
But this cannot be simplified.
But lets turn it back into a proper fraction
1 5/84