a.
7+6·(x:4-18)=25 |-7
6·(x:4-18)=25-7
6·(x:4-18)=18 |:6
x:4-18=18:6
x:4-18=3 |+18
x:4=3+18
x:4=21 |·4
x=21·4
x=84
b.
286+(a-113):5=142 |-286
(a-113):5=142-286
(a-113):5=-144 |·5
a-113=-144·5
a-113=-720 |+113
a=-720+113
a=-607
c.
[93:(x:3)-16·4]·6=186 |:6
93:(x:3)-64=186:6
93:(x:3)-64=31 |+64
93:(x:3)=31+64
93:(x:3)=95
x:3=93:95
x:3=0,98 |·3
x=0,98·3
x=2,9
