10.
0.3 r = 2.1
r = 2.1/0.3 = 21/3 = 7
Answer: 7
11.
[tex] 8 \textrm{ hours} \times \dfrac{ 5 \textrm{ dollars}}{\textrm{car}} \times \dfrac{ 12 \textrm{ cars}}{3 \textrm{ hours}} = 160 \textrm{ dollars}[/tex]
Answer: $160
12.
[tex] \dfrac{5 \textrm{ dollars}}{\textrm{week}} \times w \textrm{ weeks} = 5w [/tex]
Answer: 5w
