Question 108124
Let's call the part he invested at 18%, E, and the part he invested at 4%, F.
Then you know that,
1.{{{E+F=17000}}}
2.{{{0.18E+0.04F=1320}}}
Use 1. to solve for E in terms of F.
1.{{{E+F=17000}}}
{{{E=17000-F}}}
Now substitute that into equation 2 and solve for F.
2.{{{0.18E+0.04F=1320}}}
{{{0.18(17000-F)+0.04F=1320}}}
{{{0.18(17000)-0.18F+0.04F=1320}}}
{{{3060-0.14F=1320}}}
{{{-0.14F=1320-3060}}}
{{{-0.14F=-1740}}}
{{{F=12428.57}}}
From 1. 
{{{E=17000-F}}}
{{{E=17000-12428.57}}}
{{{E=4571.43}}}
Verify your answer using equation 2.
{{{0.18E+0.04F=1320}}}
{{{0.18(4571.43)+0.04(12427.57)=1320}}}
{{{822.86+497.10=1320}}}
{{{1319.96=1320}}} Close enough, round off error.
Good answer.
$4571.43 at 18%, $12428.57 at 4%.