First, we need to recognise which equation to use. From the Physics Equation Sheet, we can see that the correct equation here is that dQ=m*c*dT, where dQ is the Energy transfer. Using this equation, we can see that dQ = 0.50 * 4200 * -22 = -46200 J. We can check that all of our units match up too. If the water loses 46200 J, then the surroundings must gain 46200 J.