Question 30970
{{{.05 * x + .25 * .06 * x + .07 * (4*10^4 - (5/4)*x) = 2530}}}
note that (5/4)*x is (1 + 1/4)*x or x + (1/4)*x which is the amounts
that are NOT invested at 7%, so 40000 - (5/4)*x is the amount invested
at 7%
{{{.05 * x + .25 * .06 * x + .07 * 4*10^4 - .07 * (5/4)*x = 2530}}}
{{{.05 * x + .015 * x + .07 * 4*10^4 - .0875 * x = 2530}}}
{{{.065 * x + .07 * 4*10^4 - .0875 * x = 2530}}}
{{{.065 * x + 2800 - .0875 * x = 2530}}}
{{{-.0225 * x + 2800  = 2530}}}
{{{-.0225 * x  = 2530 - 2800 }}}
{{{-.0225 * x  = -270}}}
{{{ x = 12000}}}
{{{(1/4) * x = 3000}}}
{{{4 * 10^4 - ((5/4) * x) = 25000}}}
check
{{{.05 * 12000 + .25 * .06 * 12000 + .07 * (4*10^4 - (5/4)*12000) = 2530}}}

{{{600 + 180 + .07 * (25000) = 2530}}}
{{{780 + 1750 = 2530}}}
{{{2530 = 2530}}}
OK