Find the ratio of the black cell phone covers sold to the total number of cell phone covers sold last week

Just tell me how to set up the equation.

Jermaine has t subway tokens. karen has 4 more subway tokens than jermaine. raul has 5 fewer subway tokens than jermaine. which expression represents the ratio of karen's tokens to raul's tokens

The distance of a chord from the centre of a circle is 12cm and the lenght of the chord is 10cm. find the radius of the circle