SOLUTION: Solve each system using elimination. 3x+6y=42 -7x+8y= -109

Question 713534: Solve each system using elimination.
3x+6y=42
-7x+8y= -109
Answer by srinivas.g(540) (Show Source): You can put this solution on YOUR website!
given equations 3x+6y=42...................(1)
-7x+8y= -109 ..................(2)
multiply eq (1) with 4 on both sides
4*( 3x+6y)=4*42
12 x+ 24 y = 168...........................(3)
multiply eq (2) with 3 on both sides
3*( -7x+8y)=3*(-109)
-21 x 24 y = -327..............................(4)
subtract eq (4 ) from eq (3)

12 x+ 24 y -(-21 x 24 y) = 168 -(-327)
12x +24 y +21x -24 y = 168+327
33x =495
divide with 33 on both sides 33 x/33 = 495/33
x = 15
keep x = 15 in eq (1)
3(15)+6 y =42
45 +6y =42
6y =-3
y =-3/6
y =-1/2

x= 15 y =-1/2

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