In order to determine if the given traingles are similar, first consider that they have an equal angle of 90 degrees.
Now, verify if there is a constant proportion between the length of the sides of the two trangles, as follow:
WZ/MK = 21/7 = 3
ZY/SK = 12/3 = 4
Then, as you can notice, there is no a proportional relation between the sides of the triangles. Hence, you can conclude:
Are the following triangles similar? NO