Question 3050
2x + 3y = 13
 y = 3 - 2x


2x+3y=13
2x+y  =  3    
4x+4y =16

solve for X: 4x = 16-4y
	         x=16-4y/4 = 4-y=X????eq. 1
		     

now solve for Y:  y =3-[(2*(16-4x)/4]= 3 ? (8-2x)= -5+2x=Y??.eq. 2
		  		   

Now plug Y in to the eq. 1: x=4-(-5+2x)=9-2x
				3x=9, therefore X=3

Now plug X value in eq. 2: -5+2*3=Y
				Y=1


3X-Y=4
7X+2Y=18
For PART 2, U CAN USE THE MATRIX ELIMINATION USING THE CROSS PRODUCT RULE. 

SET UP MATRIX IN THE FOLLOWING FORMAT: [A]   [T] = [C]


[A]              [T]      =     [C]   

3   -1            X              4
7    2            Y             18

FIND THE DETERMINANT OF [A]= (3*2)-(-1*7)=6+7=13


NOW FIND DETERMINANT OF X: (NOW U REWRITE THE [A] MATRIX AS FOLLOW:

[A]
4      -1
18      2

DETERMINANT OF x: (4*2)-(-1*18)=8+18=26


NOW FIND THE DETERMINAT OF Y: (NOW U REWRITE [A] MATRIX AS FOLLOW:
[A]
3      4
7      18

DETERMINANT OF y: (3*18)-(4*7)=26

NOW SOLVE FOR VARIABLE X: Dx/[A] = 26/13=2
THEREFORE, X=2

NOW SOLVE FOR VARIABLE Y: Dy/[A] = 26/13=2
THERFORE, Y=2

NOW CHECK IN THE ORIGINAL GIVEN EQUATION TO SEE IF THE ANSWER IS RIGHT : 

3X-Y=4
(3*2)-2=4
4=4 , IT CHECKS

NOW CHECK THE SECOND EQUATION: 7X+2Y=18

(7*2)+(2*2)=18
14+4=18
18=18
ALSO CHECKCS...

THERFORE, X=2
     AND  Y=2