Question 362918
1.{{{0.3x - 0.2y=4}}}
2.{{{0.4x - 0.5y=-55/17}}}
If you don't like fractions or decimals, get rid of them by multiplying.
Multiply both equations by 10 to get rid of decimals.
1.{{{3x-2y=40}}}
2.{{{4x-5y=-550/17}}}
Now multiply the second equation by 17 to get rid of the fraction.
2.{{{68x-85y=-550}}}
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OK now you have 2 equations and you want to get rid of one variable.
1.{{{3x-2y=40}}}
2.{{{68x-85y=-550}}}
If you multiply the first equation by 85 and the second equation by (-2) and add them, you can eliminate {{{y}}} and solve for {{{x}}}.
{{{85(3x-2y)+(-2)(68x-85y)=85(40)+(-2)(-550)}}}
{{{255x-170y-136x+170y=3400+1100}}}
{{{119x=4500}}}
{{{highlight(x=4500/119)}}}
Now that you have {{{x}}}, use either equation to solve for {{{y}}}.
Both equations will work. 
1.{{{3x-2y=40}}}
{{{3(4500/119)-2y=4760/119}}}
{{{13500/119-2y=4760/119}}}
{{{-2y=(4760-13500)/119}}}
{{{-2y=8740/119}}}
{{{highlight(y=-4370/119)}}}