根据题意，设 x 3 = y 5 = z 7 =k，则x=3k，y=5k，z=7k，则 x+y y = 3k+5k 5k = 8 5 . y+3z 3y?2z = 5k+21k 15k?14k =26，故填 8 5 ；26．
