Data Sufficiency

I have finished about 70% of the data sufficiency questions on OG 12 and I was wondering what is the best method to solve these problems??

I dislike using complicated equations so I just utilize plugging in numbers and reasoning/logic.. However, the OG explanations for each problem relies on creating (x,y etc....) equations to solve the problem. On the more difficult problems.. it seems like this is the only way to get the answer since the OG doesn't show any other method.

Any suggestions or advice? Use more equations...? Material to look at...? I am currently hitting about 80% of my DS problems.