fix(A1): typos, style
fix(A1): typos, style

soonhokong/lean-tutorial,soonhokong/lean-tutorial,fpvandoorn/tutorial,leanprover/tutorial,Hodapp87/cs6460_project,cjmazey/fork_leanprover_tutorial,cjmazey/fork_leanprover_tutorial,avigad/tutorial,leanprover/tutorial,avigad/tutorial,Hodapp87/cs6460_project,leanprover/tutorial,avigad/tutorial,fpvandoorn/tutorial,cjmazey/fork_leanprover_tutorial,fpvandoorn/tutorial,Hodapp87/cs6460_project,soonhokong/lean-tutorial