Question 1000268
{{{X + Y =  55000}}}
{{{X = 55000 - Y}}}
{{{Y = 55000 - X}}}

{{{X *0.05 + Y*0.06 = 3090}}}
--Substitute Y in terms of X
{{{X*0.05 + (55000-X)*0.06 = 3090}}}
--Expand the 2nd expression
{{{ (X*0.05) + ((55000*0.06)-(X*0.06)) = 3090}}}
{{{ (X*0.05) + 3300 - (X*0.06) = 3090}}}
{{{ (X*0.05) - (X*0.06) = 3090 - 3300}}}
{{{ (X*0.05)-(X*0.06) = -210}}}
--Compress the expression pulling out X
{{{X(0.05-0.06) = -210}}}
{{{X(-0.01) = -210 }}}
{{{X = -210/-0.01}}}
{{{X=21000}}}
--Compute Y from X
{{{Y = 55000 - X}}}
{{{Y = 55000 - 21000}}}
{{{Y = 34000}}}

--Verify the answer
{{{X *0.05 + Y*0.06 = 3090}}}
{{{ (21000*0.05) + (34000*0.06) = 3090}}}
{{{1050 + 2040 = 3090}}}  **Correct!