how do you find JK?

Answer:
JK = 13
Step-by-step explanation:
Note that corresponding sides are congruent.
Thus ST = KL and JK = RS
Given ST = 16RS and KL = 13JK + 39, thus
KL = 13JK + 39 ( KL = ST = 16RS ), substituting
16RS = 13RS + 39 ( JK = RS )
Subtract 13RS from both sides
3RS = 39 ( divide both sides by 3 )
RS = 13
However, RS and JK are corresponding sides and congruent, thus
JK = RS = 13