Source based questions can often appear intimidating, however interpreting a source accurately is a key skill that no good historian can do without. When it comes to cartoons the first thing to do is to identify what or who the main images represent, writing down their names can be helpful. The second step you should take is to identify the source, what does this tell you about the cartoon? Avoid using vague words like biased, instead use the origin of the source to develop your answer, what point is the cartoonist trying to make? Why?
Once you have done these things futher expand your answer by bringing in contextual knowledge from things outside the cartoon. Which other factors that may not be in the cartoon itself are relevant to your answer?
Following these steps should give you a solid grasp of dealing with source based questions.