Answer:
It should take around 15 minutes
Step-by-step explanation:
2(4 - 2r) = -2(r + 5)
First, divide both sides by -2. / Your problem should look like:
Second, regroup your terms. / Your problem should look like:
Third, add 4 to both sides. / Your problem should look like:
Fourth, add r + 5 + 4 to get r + 9. / Your problem should look like:
Fifth, subtract r from both sides. / Your problem should look like:
Sixth, subtract 2r - r to get r. / Your problem should look like:

Answer:
r = 9
Hmm if I'm not mistaken, is just an "ordinary" annuity, thus
![\bf \qquad \qquad \textit{Future Value of an ordinary annuity} \\\\ A=pymnt\left[ \cfrac{\left( 1+\frac{r}{n} \right)^{nt}-1}{\frac{r}{n}} \right] \\\\\\](https://tex.z-dn.net/?f=%5Cbf%20%5Cqquad%20%5Cqquad%20%5Ctextit%7BFuture%20Value%20of%20an%20ordinary%20annuity%7D%0A%5C%5C%5C%5C%0AA%3Dpymnt%5Cleft%5B%20%5Ccfrac%7B%5Cleft%28%201%2B%5Cfrac%7Br%7D%7Bn%7D%20%5Cright%29%5E%7Bnt%7D-1%7D%7B%5Cfrac%7Br%7D%7Bn%7D%7D%20%5Cright%5D%0A%5C%5C%5C%5C%5C%5C)