(2a+3)(2分之3b+5)=2a*3b/2+2a*5+3*3b/2+15=3ab+10a+9b/2+15
(2a+3)(2分之3b+5)=3ab+10a+2分之9b＋15
(2a+3)(2分之3b+5)=3ab+2分之9b+10a+15
