Okay, here e have this:
Considering the provided information we are going to calculate how much money should be invested at each rate. So we obtain the following:
Then we will assume the amount of money at 4.3 percent interest as x, and obtain the following expression:
[tex]0.043\mleft(x\mright)+0.07\mleft(40500-x\mright)=2551.5[/tex]Let's solve for x:
[tex]\begin{gathered} 0.043x\cdot\: 1000+0.07\mleft(40500-x\mright)\cdot\: 1000=2551.5\cdot\: 1000 \\ 43x+70\mleft(40500-x\mright)=2551500 \\ -27x+2835000=2551500 \\ -27x+2835000-2835000=2551500-2835000 \\ -27x=-283500 \\ \frac{-27x}{-27}=\frac{-283500}{-27} \\ x=10500 \end{gathered}[/tex]
Finally we obtain that the amount of money at 4.3 percent interest should be 10500, and the amount of money at 7 percent interest should be (40500-10500)=30000.