A) 7s+9t-63=0
7s+9t=63
7s=63-9t 9t=63-7s
s=(63-9t)/7 t=(63-7s)/9
s=9*(7-t)/7 t=7*(9-s)/9
б) 11u+2v+22=0
11u+2v=-22
11u=-22-2v 2v=-22-11u
u=(-22-2v)/11 v=(-22-11u)/2
u=-2*(11+v)/11 v=-11(2+u)/2
в) 25r-4w-100=0
25r-4w=100
25r=100+4w 4w=100-25r
r=(100+4w)/25 w=25*(4-r)/4
r=4*(25+w)/25