ex 34
27÷[26+(6×a-7×3)÷9]+(13-2×2×3)=2
27÷[26+(6a-21)÷9]+(13-12)=2
27÷[26+(6a-21)÷9]+1=2 | -1
27÷[26+(6a-21)÷9]=1
26+(6a-21)÷9=27÷1
26+(6a-21)÷9=27 | -26
(6a-21)÷9=1|×9
6a-21=9 |+21
6a=30 |÷6
a=5
ex 35
7×(A÷4×3)+2×(A÷4×3)=18
(A÷4×3)×(7+2)=18
(A÷4×3)×9=18 | ÷9
A÷12=2
A=12×2
A=24
A=a+5b
12=a+5b
a=2, b=2
a=7,b=1
