Convert the following energy units.
905 kJ to J
2970 kcal to kJ
5.21 × 106 J to kcal
memorize the conversion units.
1000J=1kJ
1 cal= 4.1868 J
1k=1000 units
so as an example, then on the second
2970kcal(4.1868J/cal)
Then immediately check the units, to make certain the units cancel out to leave what you want.
In this case...
kcal*J/(cal) leaves kJ
do the math.