One third minus five fourths

Chip worked at the animal shelter for 6 hours each week for several weeks. he worked for a total of 42 hours. which of the following can be used to find the number of weeks chip worked at the animal shelter?

Element x decays radioactively with a half life of 8 minutes. if there are 450 grams of element x, how long, to the nearest tenth of a minute, would it take the element to decay to 37 grams?

What are the possible rational zeros of [tex]f(x) = x^4+2x^3-3x^2-4x+18[/tex]