840÷28+25×4
=30+100
=130
17+103×5-9
=17+515-9
=532-9
=523
8600÷25÷4
=8600÷(25×4)
=8600÷100
=86
37×99+37
=37×(99+1)
=37×100
=3700
[(45+525)÷5]×3
= [570÷5]×3
=114×3
=342
(28+17)×18÷9
=45×18÷9
=810÷9
=90
18.6+28.9+17.1+21.4
=(18.6+21.4)+(28.9+17.1)
=40+46
=86
29.4-17.6-5
=11.8-5
=6.8