The triangles KLH and FLH are congruent by the hypotenuse leg theorem (HL theorem for short) because KL = LF is one pair of congruent legs and LM = LM is the pair of congruent hypotenuses. This theorem only works for right triangles.
By CPCTC (corresponding parts of congruent triangles are congruent), this means we can say that the bottom two angles KHL and FHL are congruent
So,
angle KHL = angle FHL
6y = 4y+18 ... substitution
6y-4y = 4y+18-4y .... subtract 4y from both sides
2y = 18
2y/2 = 18/2 ... divide both sides by 2
y = 9
Answer: 9
