Calculate the energy provided by a slice of bread containing 2 g of protein, 1 g of fat, and 20 g of carbohydrate. record your answer using whole number.

The energy provided by equal amounts of carbohydrates and fats are not the same. This means that 1 g of carbohydrates will give out a different value of calories than 1 g of fat.
Proteins and carbohydrates both give 4 calories per gram,
Fats give out 9 calories per gram,
Therefore energy given by each food type is as follows;
proteins- 2 g x 4 calories/g = 8 calories
Carbohydrates- 20 g x 4 calories/g = 80 calories 
Fats- 1 g x 9 calories/g = 9 calories
Total energy - 8+80 + 9 = 97 calories 
1 cal - 4.18 kJ
Therefore 97 calories - 4.18 kJ/cal x 97 cal = 405 kJ