sorry, but i can only TRY to help u.
if the spag.(56g) only contains carbohydrate, protein and water and ifcarbohydrate, protein are the only source of energy. Then the 7 g protein provides 28 kcal, but the 56g spag. gives 200kcal,
Thus the energy provided by carbo =(200-28)kcal=172kcal,but since carbo givs 4 kcal/g, carbo in the spag weighs 172/4 g= 43g
Thus carbo and protein 2gether weigh 43g +7 g = 50g, assuming the only other component is water, it must weigh 56g-50g=16g
thus % of H20 by mass=16/56 .100%=25%
PS plz check for calculation errors, also i am only attempting, i do not garantee a correct answer, the other questions can be solved in similiar manner