(5/12)*49+51*(7/12)
=(5/12)*7*7+51*(7/12)
=(7/12)*5*7+51*(7/12)
=(7/12)*35+51*(7/12)
=(7/12)*(35+51)
=(7/12)*86
=(7/12)*(84+2)
=(7/12)*84+(7/12)*2
=49+7/6
=50+1/6
=50又6分之1