Agree with somebody,/Agree on something,
it takes somebody sometime to do something/,spend sometime in doing something.
agree 英[əˈgri:] 美[əˈɡri]
vt. 同意,赞同;
vi. [语] 一致,符合; 商定,约定; 意见相合; (气候、食物等) 适宜;
vt. 同意,承认; 使和谐一致; 认为正确无误;
agree本身就是“同意、赞同”的意思,
如果说“赞同某人”,可以用agree with sb.这个短语
除此之外,consent to也表示“赞同”