victor has invested $4000 into two accounts, part at 5% simple interest and part at 9% simple interest. Find how much he invested at each rate if the total interest after 1 year is $311.
Simple interest is $\displaystyle P=P_0+P_0rt$
So say $\displaystyle A=P_0+P_0(.05)(1)$ and $\displaystyle B=Q_0+Q_0(.09)(1)$. This describes the two investment conditions you listed.
Also we know that $\displaystyle Q_0+P_0=4000$ and $\displaystyle P_0(.05)(1)+Q_0(.09)(1)=311$
Can you take it from here?
Hello, trapt2006@sbcglobal.net!
Try some baby-talk . . .
Victor has invested $4000 into two accounts, part at 5% and part at 9%.
Find how much he invested at each rate if the total interest after 1 year is $311.
He invested $\displaystyle x$ dollars at 5%.
. . This will earn: $\displaystyle 5\% \times x \:=\:0.05x$ dollars in interest in one year.
He invested the rest $\displaystyle (4000 - x)$ at 9%.
. . This will earn: $\displaystyle 9\% \times (4000 - x) \:=\:0.09(4000-x)$ dollars in interest in one year.
His total interest is $311: .$\displaystyle 0.05x + 0.09(4000 - x) \:=\:311$
and there is our equation!