7.5×[63.9÷(7-2.5)]
=7.5×(63.9÷4.5)
=7.5×14.2
=106.5
26.19＋0.91÷(3.6-2.9)
=26.19+0.91÷0.7
=26.19+1.3
=27.49要简便