Question

substitution method
4x + y = 16
7x +3y = 9
@Kainui

Answer 1

so far I have these steps completed...
4x + y =16
4x + y = 16 + 4x
7x 3(16 + 4) = 9
7x + 48 + -12) = 9

Answer 2

@dan815
@TheSmartOne

Answer 3

umm?

Answer 4

4x + y = 16
7x +3y = 9
do this :
4x + y = 16
therefore,
y = 16 - 4x now substitude

Answer 5

I did that already...look at the response after my post

Answer 6

that is
7x + 3(16 - 4x) = 9

Answer 7

Followed so far?

Answer 8

Do I take 48 from each side?

Answer 9

wait

Answer 10

i made a mistake

Answer 11

I know after this step I have to do the distributive law...which means 7x + -12 = 5x...then I take 48 from each side which leaves me 31?

Answer 12

The best way to do these, is to first look at the problem and isolate the variable that doesn't have a constant, right off the bat, we know that y= 16- 4x from the first equation. WE can use this, and sub in for y in the second equation:

7x + 3(16-4x) = 9
7x + 18 - 12x = 9
-5x + 18 = 9
-5x = -9
x = 9/5

Now sub x in the first equation to solve for y.

4(9/5) + y = 16
(36/ 5) + y = 16
y = 16 - 36 / 5
y = 8.8

Answer 13

Let me know if you need a further explanation.

Answer 14

its 48 not 18

Answer 15

Woah, I made a huge mistake. 3*16 is not 18..

Here's a redo.
7x + 3(16-4x) = 9
7x + 48 - 12x = 9
-5x = -39
x = 39/5

Answer 16

Sub in the second, we get
4(39/5) + y = 16
y = -15.2

Answer 17

x= 7.8
y= -15.2 :)