Respuesta :

devishri1977

Answer:

Step-by-step explanation:

x + y = 4  ---------------(i)

x = 4-y

7x + 9y = 42 -----------(ii)

Plug in x = 4-y in equ (ii)

           7*(4 - y) + 9y = 42

             28 - 7y +9y = 42

                   28 + 2y = 42

                           2y = 42 - 28

                           2y = 14

                            y = 14/2

y = 7

x = 4 - y

x = 4 - 7

x = -3

dillonliyanage

Answer:

use system of equations

x+y=4

7x+9y=42

if we want to solve for y first

then multiply the first equation by 7 to cancel out x

 7x+7y=28

- 7x+9y=42

-2y=-14

y=7

to solve for x just input y into the equation

choose any equation u like from one of the two

x+7=4

x=4-7

x=-3