15 kJ of heat is given to 0.40 kg of aluminium, 0.40 kg of iron and 0.40 kg of copper…

Step 1. Aluminium. $\dfrac{15\,000\ \text{J}}{0.40\ \text{kg} \times 900\ \text{J kg}^{-1}\text{K}^{-1}} = 41.7\ \text{K}$.

Step 2. Iron. $\dfrac{15\,000\ \text{J}}{0.40\ \text{kg} \times 450\ \text{J kg}^{-1}\text{K}^{-1}} = 83.3\ \text{K}$.

Step 3. Copper. $\dfrac{15\,000\ \text{J}}{0.40\ \text{kg} \times 385\ \text{J kg}^{-1}\text{K}^{-1}} = 97.4\ \text{K}$.