If c varies directly as d-3, and if c=16 when d=7, find c when d=10

Abox contains 1 plain pencil and 4 pens. a second box contains 5 color pencils and 5 crayons. one item from each box is chosen at random. what is the probability that a plain pencil from the first box and a color pencil from the second box are selected? write your answer as a fraction in simplest form.

This is about circle theorems. someone asap : (

The owner of the plant nursery where you were tells you to fill 350 ml bottles from a 30 l from a fertilizer