SOLUTION: My pre-algebra teacher,Mrs.Sanders, assigned a worksheet called Linear Equations and Inequalities.Then below that it says system of Equations: Substitution Method. The example is

Question 36117: My pre-algebra teacher,Mrs.Sanders, assigned a worksheet called Linear Equations and Inequalities.Then below that it says system of Equations: Substitution Method.
The example is as follows;
x-5y=10
-2x=y=7 then arrow points over y=2x=7
x-5(2x+7)=10
x-10x-35=10
-9x-35=10
-9x=45
x=-5 then it says th solutionis (-5,-3)
And I have no idea how they got this,so can you help me out?
Answer by qwe123a(7) (Show Source): You can put this solution on YOUR website!
nope
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