Question

Solve. (The answer is supposed to be in order pairs.) [Image Below.]

Answer 1

Answer:

$\left \{ {{x=-3} \atop {y=7}} \right.$

Step-by-step explanation:

Hi mate!

We know that $y=4-x$!!!

So it's correct to say $7x+9(4-x)=42$.

$7x+36-9x=42$

$-2x=6$

∴ $x=-3$

We have x, now put it in $y=4-x$.

∴ $y=7$

∴$\left \{ {{x=-3} \atop {y=7}} \right.$

Answer 2

Answer:

$x + y = 4 \\ 7x + 9y = 42$

Multiply Eqn 1 by 7

and Eqn 2 by 1 ....you will get

$7x + 7y = 28 \\ 7x + 9y = 42$

Now, just substract these new Equations and after that u will get ____

$- 2y = - 14 \\ 2y = 14 \\ y = 7$

Now put the value of y in Eqn 1

$x + y = 4 \\ x +( 7 )= 4 \\ x = 4 - 7 \\ x = - 3$

So, the Answer is (-3,7)