Note: You may need the molecular weight of a compound in order to solve some questions.
Simply read the m/z value for the decently sized peak on the right hand side of the spectrum. In the below example, the answer is 32. Ignore tiny peaks like the one at m/z 33. Sometimes, you will get the answer wrong – but you will only be 1-2 amu from the true value. That should be enough information for you to solve these questions.