Question 160327
<font size = 7 color = "red"><b>Edwin's solution:</font></b>
hi please help me thank you very much.   Which of the following is an intermediate step if the given equations are to be solved by elimingating one unknown by addition?
{{{system( 5x + 5Y = 1,  3x - 8y = 5)}}}   
the answers are 
A){{{system(40x + 40y =8,  15x - 40y = 25)}}}
B){{{system(15x + 15y = 3,  15x - 40y =25)}}}
C){{{system(5x + 5y = 1,   y = (3x - 5)/8)}}}
D){{{system(x = (1 - 5y)/5, x =(5 + 8y)/3)}}}  

<pre><font size = 4 color="indigo"><b>
The correct answer is A) because
when added vertically, the terms {{{matrix(1,2,"+",40y)}}} and {{{-40y}}}
will cancel out like this:

A){{{system(40x + cross(40y) =8,  15x - cross(40y) = 25)}}}

and the sum adding vertically will be the equation:

   {{{55x}}} =  {{{33}}}   

which is easily solved for {{{x}}}.

Edwin</pre>