Number 7:
Downloading 3 songs a day means that you have [tex] 3n [/tex] after [tex] n [/tex] days.
So, on day 15 you will have
[tex] 3\cdot 15 = 45 [/tex] songs
You will have more than 40 songs when
[tex] 3n>40\iff n>\dfrac{40}{3} = 13.\overline{3} [/tex] days
So, the first integer bigger than our value is 14.
Number 8:
To compute the volume of prisms like these (all sides are perpendicular), you simply have to multiply the dimensions:
[tex] V = 5\dfrac{3}{5}\cdot 2\dfrac{1}{8} \cdot 4\dfrac{2}{3} = \dfrac{1937}{120} \approx 16.14 [/tex] cubic feet
Assuming that the sides are written with mixed fraction.
