упростите: а)(1/5+1/5+1/5)×1/3 б) (2/7+2/7+2/7+2/7)×21/8

а)3/5×1/3=1/5
б)8/7×21/8=3

(1/5+1/5+1/5)*1/3=3/5*1/3=1/5
(2/7+2/7+2/7+2/7)* 21/8= 8/7*21/8=3