Your equation is correct.
[tex] C(x) = \dfrac{10}{3} x [/tex]
Now to find the number of mints, let C(x) equal 180 and solve for x.
[tex] C(x) = \dfrac{10}{3} x [/tex]
[tex] 180 = \dfrac{10}{3} x [/tex]
[tex] 540 = 10x [/tex]
[tex] 54 = x [/tex]
[tex] x = 54 [/tex]
Answer: There are 54 mints in the box.
