7a – b = 15a, for a does anyone have a clue what this is

Adrawer contains 12 identical white socks, 18 identical black socks and 14 identical brown socks. what is the least number of socks you must choose, without looking, to be certain that you have chosen two socks of the same colour?

Big boi and travis scott are performing at the super bowl. travis scott is 62 years younger than twice big boi’s age. the sum of their ages is 70 years old. use b to represent big boi’s age. write and solve an equation.

Math it's appreciated. (picture provided)