56 is 80% of blank. what is the blank supposed to be?

Rewrite the following quadratic functions in intercept or factored form. show your work. f(x) = 3x^2 - 12

Will mark brainliest! ( explain the answer too, it can be one sentence)

Cherie works in retail and her weekly salary includes commission for the amount she sells. the equation s=400+0.15c models the relation between her weekly salary, s, in dollars and the amount of her sales, c, in dollars. interpret the slope of the equation.