2( х + 5 ) = 9 - 3( 4 + y )
21 + 6x + 4y = 4( 2x + 5 )
Решение
2х + 10 = 9 - 12 - 3y
2x = - 10 + 9 - 12 - 3y
2x = - 13 - 3y
x = - 6,5 - 1,5y
21 + 6x + 4y = 8x + 20
8x - 6x = - 20 + 21 + 4y
2x = 4y - 1
4y - 1 = - 13 - 3y
7y = - 12
y = - 1 ( 5/7 )
2x = 4•( - 12/7 ) - 1 = - 48/7 - ( 7/7 ) = - 55/7
x = - ( 55/7 ) : 2 = - 55/14 = - 3 ( 13/14 )
Ответ ( - 3 13/14 ; - 1 5/7 )