15с+3с-12=78 (6y+14)/2+15=40 16x+5=133 42k-28k+180=600
18с=78+12 3y+7+15=40 x=(133-5)/16 42k-28k=600-180
с=(78+12)/18 3y=40-15-7 x=8 14k=420
с=5 y=(40-15-7)/3 k=420/14
y=6 k=30
X^2*(x-3)-4(x-3)=0
(x^2-4)*(x-3)=0
(x-2)*(x+2)*(x-3)=0
x-2=0
x+2=0
x-3=0
x1=-2
x2=2
x3=3
3х+19х-21х-4=17
22х-21х=17+7
х=21
25х+4х-28х+7=28
29х-28х=28-7
х=21
7×(2,3+0,8×0,4)+1,9×0,4=20,64