Solve by using elimination method 0.3x-0.2y=4 and 0.5x+0.5=85/19?

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Oddman answered
Multiply the first equation by 5 and add the twice the second equation.
  5(0.3x - 0.2y) + 2(0.5x + 0.5y) = 5(4) + 2(85/19)
  1.5x - 1.0y + 1.0x + 1.0y = 20 + 170/19
  2.5x = 550/19
  x = (550/2.5)/19 = 220/19

Substituting this value into the second equation, we get
  0.5(220/19) + 0.5y = 85/19
  110/19 + 0.5y = 85/19    (eliminate parentheses)
  0.5y = -25/19    (subtract 110/19)
  y = (-25/0.5)/19 = -50/19    (divide by the y coefficient and evaluate)

The solution is (x, y) = (220/19, -50/19).

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