1)
[(a+260:2)x3+4]=1985:5
[(a+260:2)x3+4]=397
(a+260:2)x3=397-4
(a+260:2)x3=393
a+260:2=393:3
a+260:2=131
a+130=131
a=131-130
a=1
2)(b:5-4):3-260:2=1
(b:5-4):3-260=2x1
(b:5-4):3=260+2
b:5-4=262x3
b:5-4=786
b:5=786+4
b:5=790
b=790x5
b=3950
3){[(7-3)x5-2+3]:7+9}:c=4
[(4x5-2+3):7+9]:c=4
[(20-2+3):7+9]:c=4
(21:7+9):c=4
(3+9):c=4
12:c=4
c=12:4
c=3
(