3.6*31又5分之2+43.9*6又5分之2
=3.6*31+43.9*6+3.6*2/5+43.9*2/5
=6*18.6+43.9*6+（3.6+43.9）*2/5
=6*（18.6+43.9）+47.5*2/5
=6*62.5+19
=375+19
=394