8pr=7p3+3*7p2?, find r?

8Pr=7P³ +3*7P² 8Pr = (7!/4!) + 3(7!/5!) 8Pr =7*6*5 + 3(7*6) 8Pr = 336 8Pr = 8*7*6 8Pr = (8)(8-1)(8-2). [since; nP³ = (n)(n-1)(n-2)] r = 3