An exothermic reaction releases 86.5 kJ. How many kilocalories of energy are released?
This problem is just a unit conversion, so you need to know the definition of a calorie. A calorie is a unit of energy equal to 4.184 J. This is the energy required to heat up one gram of water by one degree celsius at a pressure of one atmosphere. If 1 cal = 4.184 J, then 1000 cal = 4184 J.
Divide both sides by 4.184 to get kJ in terms of kcal.
Now you have your conversion factor and just need to multiply both sides by 86.5.