Is there like any image to see how big are the posts?
Isolate the x and the 2 from the top of the equation, then cancel those out from the bottom, then divide out the -1. after that you are left with -6x²+2x-4
175 students walk to school. 7+5=12 and 420 divided by 12 is 35. I checked how I did it was correct because of 5*35+7*35=420. Then I found the product of 5*35 which is 175.