Hi Everyone!
I'm new to this Forum and I came here so I can score high on the GMAT and improve my skills needed to be successful. As I'm running through the Princeton Review GMAT book . I found Im still not grasping the "plugging in " concept in the Algebra section of the book are there any resources online or maybe a list on this forum that I missed(I searched believe me

) which have numerous questions like these so I can really solidify my understanding on this particular concept?
Thanks community!