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Matth help!

0.3x-0.5y=-1 3/5x-1/10y=-11

I need to use substitution, and I know how too, but I cant figure this one out. The solution is suppose to be (-20,10). I need to show the work! Please help!

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Answer #1

This is just a simultaneous equation problem.

For your first equation ie 0.3x - 0.5y = -1, re-arrange it to make why the subject (you could also make x the subject too, but let’s do it this way)

0.3x - 0.5y = -1 0.3x + 1 = 0.5y 0.6x + 2 = y [Multiplying both sides by 2]

then sub y = 0.6x +2 into the other equation you have ie (3/5)x - (1/10)y = -11

(3/5)x - (1/10)y = -11 (3/5)x - (1/10)(0.6x + 2) = -11 (3/5)x - (0.06x + 0.2) = -11 0.6x - 0.06x - 0.2 = -11 [ (3/5) = 0.6] 0.54x = -10.8 therefore x = -10.8 / 0.54 = -20

Then substitute x = -20 into y = 0.6x + 2 y = 0.6x + 2 = 0.6(-20) + 2 = -10

therefore , x= -20 and y =-10

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