Question

What the value of x in 3x+4y=30 -9x+y=-12

Answer 1

Answer:

hope it helps you

Step-by-step explanation:

pls do tell me it works or not mark me as brainlist

Answer 2

Answer:

x = 2

y= 6

Step-by-step explanation:

3x + 4y = 30 (make this equation 1)

-9x + y = -12 ( and this ne equation 2)

simplify eq. 2

from -9x + y = -12 to y = -12 + 9x ( the symbol changes when you move the no.)

so now y = -12 + 9x is our new eq. lets call it eq. 3. now lets only focus on eq. 1 and 3 only. ( because eq. 3 is the same with eq. 2)

3x + 4y = 30 (eq. 1) and y= -12 +9x (eq. 3)

now you can easily substitute eq. 3 into eq. 1.  

y= -12 + 9x into the y eq.1

3x + 4 ( -12 + 9x) = 30          

3x + 4(-12) + 4(9x) = 30

3x -48 + 36x = 30

3x + 36x = 30 + 48

39x = 78

x = 78/39

x = 2

Just for extra knowledge, now lets try y.

use the same method and substitute x into eq. 3

y = -12 + 9x

y = -12 + 9(2)

y = -12 + 18

y = 6