1. 77x(77x4-77-77:7-77)-77x7=
77x(308-77-11-77)-539=
77x143-539=11011-539=10472
2.
27:[26+(6x5-7xa):9]=1
27:[26+(30-7xa):9]=1
26+(30-7xa):9=27
(30-7xa):9=27-26
(30-7xa):9=1
(30-7xa)=9
7xa=30-9
7a=21
a=21:7
a=3
3.
1000-[5+2x(100+yx4)-124:4]=754
1000-[5+2x(100+yx4)-31]=754
[5+2x(100+yx4)-31]=1000-754
5+2x(100+yx4)-31=246
2x(100+yx4)=246-5+31
2x(100+yx4)=272
100+yx4=272:2
100+yx4=136
yx4=136-100
yx4=36
y=36:4
y=9
4.
z:[960:3+13x5-(3x100+8x10)]=123 rest 4
z=[960:3+13x5-(3x100+8x10)]x123+4
z=[320+65-(300+80)]x123+4
z=(385-380)x123+4
z=5x123+4
z=615+4
z=619