The odds of choosing one black ball from an urn are 8 to 13. what is the probability of getting a black ball?

Can someone check if i did this correct. it’s number 4 if you’re wondering.

Is this a polynomial function? i need to know asap

Abag of jelly beans contain 13 pink, green, 20 yellow, 10 black, 7 red, and 11 orange jelly beans. approximately what percent of the jelly beans are pink and yellow?