You can find undergraduate courses grade distribution here (click Undergraduate Grades tab) – https://www.brown.edu/about/administration/institutional-research/factbook/courses
Please note that students at Brown can drop a course about a week before the final exam without implications. So the grade distribution you see in the courses factbook does not mean that it is easy to get an “A”. If you watch the video I have linked above, you will see that a large number of Brown premed students take organic chemistry in the spring semester of freshman year (only offered once a year). People who don’t do well in orgo can move on early (do CS etc.) or take a step back (take it again next year) without implications to their future endeavors. You only need 30 courses to graduate; so theoretically you can drop(fail) a course twice if you keep a 4-course per semester load at Brown.