How much alcohol must be burned to generate

279kj of heat to warm the water as described in
problem 3? (60F to 180F)

I've seen where they say the answer is

(mass of alcohol)(heat ofcombustion)=279

and you solve for mass. However how am I to know which heat of combustion to use. The only values we are given are some heat of formation.

You've only posted parts of the problem.

You must first convert 60 F to C and 180 F to C.
Next you write the equation and balance it.
Third you use the heats of formation to find the heat of combustion for a mole of the material. If you will post the entire problem I can go through the process. I think what you show as the "ANSWER" is a part of an answer I gave earlier. I think you have misinterpreted the answer and the problem.