13.) [tex]k = \frac{mv}{2}[/tex] means that k is half of the product of m and v. If this is true, it can also be said that k is twice as much as the product of m and v, so this becomes [tex]2k = \frac{mv}{2} * 2[/tex] --> [tex]2k = mv[/tex]. If v is m times greater than 2k, you can rewrite this as [tex]\frac{2k}{m} = \frac{mv}{m}[/tex] which means that [tex]v = \frac{2k}{m}[/tex].
14.) [tex]A = P + Prt[/tex]
--> [tex]A - P = Prt[/tex]
---> [tex]\frac{A - P}{Pt} = r[/tex]
