Question 238838
a. 
   X + Y = 6  
-(2X + Y = 8) SUBTRACT.
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-X=-2
X=2 ANS.
-2+Y=6
Y=6+2
Y=8 ANS. 
2*2+Y=8
4+Y=8
Y=8-4
Y=4 ANS.
PROOF:
2+4=6
6=6
2*2+4-8
4+4=8
8=8

b.
7X + 3Y = 14 MULTIPLY BUY -3 & ADD
5X + 9Y = 10
-21X-9Y=-42
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-16X=-32
X=-32/-16
X=2 ANS.
7*2+3Y=14
14+3Y=14
3Y=14-14
3Y=0
Y=0 ANS.
PROOF:
5*2+9*0=10
10=10

c.  
4X + Y = 16 MULTIPLY BY -3 & ADD
2X + 3Y = 24
-12X-3Y=-48
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-10X=-24
X=-24/-10
X=2.4 ANS.
4*2.4+Y=16
9.6+Y=16
Y=16-9.6
Y=6.4 ANS.
PROOF:
2*2.4+3*6.4=24
4.8+19.2=24
24=24
d.
12X + Y = 25 MULTIPLY BY 2 & ADD .
8X - 2Y = 14
24X+2Y=50
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32X=64
X=64/32
X=2 ANS.
12*2+Y=25
24+Y=25
Y=25-14
Y=1 ANS.
PROOF:
8*2-2*1=14
16-2=14
14=14