Question 314181
Let A be the amount at 6% and B be the amount at 7%.
Total amount
1.{{{A+B=4000}}}
Total interest
{{{0.06A+0.07B=264}}}
{{{6A+7B=26400}}}
Multiply eq.1 by (-6) and add to eq. 2,
{{{-6A-6B+6A+7B=-24000+26400}}}
{{{highlight_green( B=2400)}}}
Then from eq. 1,
{{{highlight_green( A=1600)}}}
He has $1600 invested at 6%, $2400 invested at 7%.