Use the heat of fusion formula:
The heat of fusion of water is 333.6 J/g, which means that it takes 333.6 joules of energy to melt one gram of ice.
Since we have 91.0 grams of ice, plug 91.0 into the formula and multiply by 333.6.
However, this answer is in joules, so we need to convert to kilojoules.
1000 joules = 1 kilojoule
30357.6 joules = 30.3576 kilojoules
The answer, expressed to 3 significant figures, is 30.4 kilojoules.