Do similar calculations for the second one, 30 g O = 30/16 = 1.875 moles reacting with 100-30 = 70 g metal. So the moles of metal will be 70/56 = 1.25 moles
so the ratio of metal to oxygen is 1.25:1.875, divide by the smaller number which is 1.25, you get 1:1.5, you need to get to whole numbers, so it will be 2:3, therefore the formula will be M2O3
4. Wt of sulfur = 3.4 g or 3.4/32 = 0.106 moles. Molecular mass of insulin will be then assuming it contains one mole of sulfur 100/0.106 = 943.4
5. same as no. 3, you should be able to calculate by now, but here it is only for you to check your answer. wt of 1 L of acid = 1294 g, acid wt will be 49 g, so wt of water will be 1294-49 = 1245 g (or mL), so you have 49 g of acid in 1245 ml water, so 1 L water will contain 49*1000/1245 = 39.36 g.
Then molarity will be wt/mol wt = 39.36/98 = 0.4 M
Please understand the concept of how to solve these types of problems, rather than blinding copying this info in your assignment. That way it will help you out a lot in the future, especially when writing the exams