\[\frac{83.4+84.5}{2}=\frac{167.9}{2}=83.95.\]
\[\frac{0.2+0.3+0.4}{3}=\frac{0.9}{3}=0.3.\]
\[\frac{2.23+2.26+2.34+2.07}{4}=\frac{8.90}{4}=2.225.\]
\[\frac{6.276+5.864+7.223+9.106+8.728+3.003}{6}=\frac{40.2}{6}=6.7.\]
Ответ: а) 83,95; б) 0,3; в) 2,225; г) 6,7.