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if 4x + 3y + 7m = 11.5 and 3x + 1y + 9m = 10 ; what is the sum of 1x + 1y + 1m

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2 Answers

Multiply the first equation by 2, subtract the second equation from it, divide the result by 5:
 
 (8x+6y+14m)=23
-(3x+y+9m)=-10
  5x+5y+5m=13
 
x+y+m=13/5.
From the second equation y=10-3x-9m; Plug it into the first equation to get:
 
4x+3(10-3x-9m)+7m=-5x-20m+30=11.5 From this we obtain upon simplification:
 
x+4m=3.7 Thus x=3.7-4m; Plug it in the expression for y to obtain:
y=10-3x-9m=10-3(3.7-4m)-9m=-1.1+3m
 
So, we have:
 
y=3m-1.1
x=-4m+3.7
 
Therefore, x+y+m=3m-1.1-4m+3.7+m=2.6

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