Find the length of the missing side

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

Which of the following vectors are orthogonal to (2,1)? check all that apply

Cd is the perpendicular bisector of both xy and st, and cy=20. find xy.