GMAT Quantitative Section | Re: Good to great？！48-50-51？

Hi,

I tried twice GMAT and got 50 and 48 respectively, I searched some of questions in different forums only found that some of the challenge questions not really challenging to me?

can somebody advise me how can I improve my math scores from to 51/52? any resources, courses can recommend? any methodologies?

Many thanks,

Michael