Answer
$$m_{Fat} = 37 \space g$$
Work Step by Step
$$Energy_{Carbohydrate} = 13 \space g \times 4 \space kcal/g =52 \space kcal$$
$$Energy_{Protein} = 5 \space g \times 4 \space kcal/g =20 \space kcal$$ $$E_{Carbohydrate} + E_{Protein} + E_{Fat} = 405 \space kcal$$ $$E_{Fat} = 405 \space kcal - 52 \space kcal - 20 \space kcal$$ $$E_{Fat} = 333 \space kcal$$
$$E_{Fat} = m_{Fat} \times 9 \space kcal/g$$ $$333 \space kcal = m_{Fat} \times 9 \space kcal/g$$ $$\frac{333 \space kcal}{9 \space kcal/g} = m_{Fat}$$ $$m_{Fat} = 37 \space g$$
