in a class, 12 pupils are in a computer class and 3/4 of the remaining pupils are in the science club. If 1/5 of the pupils are neither in the computer nor science club, how many pupils are there in the class?

C. as you can see, the small triangle in the larger figure takes up two blocks, while the small triangle in the small figure takes up only one. you are left with a and c. 

a 90 degree rotation doesn't make sense because the triangles will be facing east and southeast.