=3/17×5.4+0.37×30/17+9.1×14/17
=3/17×5.4+0.37×10×3/17+9.1×14/17
=3/17×（5.4+3.7）+9.1×14/17
=3/17×9.1+9.1×14/17
=（3/17+14/17）×9.1
=1×9.1
=9.1