Because this triangle is an isosceles, we know that angle M and angle L are equal (as shown by the diagram)
So, we make the two values equal
5y-19=56
Take 19 to the other side as a positive
5y=75
y is equal to 15
But, we aren't done yet as the question asks us to find the value of k
So, we do
5*15-19+56+K=180
112+K=180
Take 112 to the other side as a negative number
180-112 is 68
So, angle K is equal to 68 degrees