Help with 19, 19a, and 19b please

Given this information, which expression must represent the value of b?

Which equation represents the partial sum of the geometric series?

Im gonna fail 7th grade selective breeding 1. creates offspring which are genetically identical to the parent 2. is the process of breeding only organisms with desirable traits 3. involves the removal of the nucleus of a cell 4. combines traits from organisms of different species