ex 1 100-(8×8÷8)=92
= 100-64÷8
=100-8
= 92
(10+13)+(36÷9-21÷7)=24
=(10+13)+4-3
=23+1
=24
(5×4)+(45-2×9×6×0=65
=20+45-0
=65-0
=65
164+(100-9÷9-5×10)=213
=164+100-1-50
=264-51
=213
5×(10÷10×10)+(8×3-23)=
=5×10+24-23
=50+1
=51
ex2 100÷a=10
a=100÷10
a=10
9×b=45
b=45÷9
b=5
c÷3=7
c=7×3
c=21
d×6=42
d=42÷6
d=7