Х2 + 4х - 12 - 3х = х2 - х
х2 + 4х - 12 - 3х - х2 + х = 0
2х-12=0
2х=12
х=6
15х(-3(19-18))+3х=х+90+2х
15х(-57+54х)+3х=х+90+2х
-855х+660х^+3х=х+90+2х
660х^-855х+3х-х-2х=90
660х^-855х=90
15х(44х-57)=90
1)15х=90 2)44х-57=90
х=6 44х=90-57
44х=33
х=3/4
10м-9м2дм-25см =1000см-920см-25см=55см
5x-4y=20
-4y=20-5x
4y=5x-20
y=5x-20/4