Question

substituição
a) x+y=7
6x-4y=12

b)x-y=5
x-2y=1

Answer 1

a) x= 7-y

6x - 4y = 12
6*(7-y) - 4y = 12
42 - 6y -4y = 12
-10y = 12-42
y = 30/10
y = 3

achando x

x+y = 7
x = 7 - 3
x = 4

b) x= 5+y

x- 2y = 1
5+y - 2y = 1
-y = 1-5
y = 4

achando x

x = 5+ y
x = 5 + 4
x = 9

Answer 2

  x + y =   7 >>>>>> x =  7 - y *****
6x - 4y = 12
6 ( 7 - y) - 4y = 12
42 - 6y - 4y  = 12
-10y = = 12 - 42
-10y = - 30
10y = 30
y = 30/10 = 3 ****

x = 7 - 3 
x = 4 *****




x - y   = 5 >>>>>>>   x =  5 + y ****
x - 2y = 1
( 5 + y ) - 2y   = 1
-y= 1 - 5
-y = -4
y = 4 ****

x = 5 + 4
x = 9 ****