If two fifth of a number is four what is the number

I’m stuck on this i don’t understand.

Using the quadratic formula find the zeros of the given polynomial -5x^2+3x-11

In the following situation, determine whether you are asked to determine the number of permutations or combinations. then do the calculation how many ways are there to pick a starting five from a basketball team of twelve members? a. permutation; ps - 2520 b. combination; 1c, - 792 c. combination: 2cs - 2520 d. permutation; ps - 95040