If you answer both questions correctly, you will find out the numerical code to decrypt this paragraph from Minerva McGonagall's letter:
Xt bj ymtzlmy dtz htzqi it f lwjfy xjwanhj yt tzw rflnh xhmttq nk dtz flwjj yt wjanjb ymj lwfrrfynhfq xywzhyzwj, athfgzqfwd fsi jcfhy uwtszshnfynts tk ymj jshmfsyrjsyx zxji gd tzw fuuwjsynhj rflnhnfsx.