Answers

2015-06-09T19:55:23+05:30
First adding the equations
21x +47y = 110
47x + 21y=162
                                        
68x+ 68y=272
x + y =4 ......(i)
now subracting the equation
21x +47y = 110
47x + 21y=162
-        -         -         
-26x-26y=-52
-x-y=2...(ii)
now add both and solve further



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2015-06-09T19:59:46+05:30
Add both the equations             
 21x + 47y = 110   {1}                        = 68x + 68y = 272
 47x + 21y = 162   {2}                        = 68(x + y) = 272
                                                    = x + y = 272 - 68 = 204          {3}
subtracting {2} from{1}
(21x + 47y) - (47x + 21y) = 162 - 110
 -x + y = 52    {4}
adding the {3} and {4}
x + y + (-x + y) = 204 + 52
2y = 256
y = 256/2 =128
substituting it in any equation {1} {2} {3} {4} 
we get  x = 76
the solution of the pair of equations is [x ,y] is [76 , 128]
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