Convert the following energy units.

Question

905 kJ to J

2970 kcal to kJ

5.21 × 106 J to kcal

Answer 1

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.