Choose the congruence theorem that you would use to prove the triangles congruent for the last one sss sas asa aas

We already discussed the first triangle which should be HL :D! 

For the second one it should be ASA (Question 17)
ASA states if two angles and the included side of one triangle are congruent to the corresponding parts of another triangle, then the triangles are congruent.
As for question 16 the question is cut off but assuming it is the same thing it will most likely be SSS since it states if three sides of one triangle are congruent to three sides of another triangle, then the triangles are considered congruent.
For question 18 or what is above it I cannot be too sure...
AS for the one that is 18 or below it with just SSS and SAS. I would say it would be SAS since it states that if two sides and the included angle of one triangle are congruent to the corresponding parts of another triangle, then they are congruent.

The length is 23 and y because you add them together