The third step's reason is given. Then you must make <QRP and <SRT congruent because all right angles are congruent. Then you have two angles in each triangle congruent and can thus prove the triangles congruent by AA.
The first blanck answer is 3 because 3/4 is also known as .75 as a decimal and if you do 3 divided by .75 you get 4 meaning 4 is your second black answer