Question

In the square pyramid shown below h=12 and b=18 what is the length of the slant height?

Answer 1

its D. 15 cm. 
You were on the right track, i can see your work but if B=18 D cannot =18 too because D is half B. so its 12² + 9² = 15cm

Answer 2

I think the answer would be 15 Cm