John used 1 3/4 kg of salt to melt the ice on his sidewalk.
Amount salt used to melt ice = 1 3/4
Express the mixed fraction as :

He then used another 3 4/5 kg on the driveway
Express mixed frcation as :

So, the amount of salt left = Total amount of salt - Amount of salt used on the driveaway + Amount of salt usde deuring drive way
From the given question :
he originally bought 10 kg of salt
Total amount of salt = 10kg
the amount of salt left = Total amount of salt - Amount of salt used on the driveaway + Amount of salt usde deuring drive way
T = 10 - 7/4 -19/5
T= 89/20
She left with 89/ 20 Unit kg weight
ANswer : 89/2-0