You are told that the average (mean) is 565 and the standard deviation is 75 so the "standard score" corresponding to 500 is $\frac{500- 565}{75}= -0.87$ (not "-87"). Using http://math.arizona.edu/~rsims/ma464...ormaltable.pdf, I get P(z< -0.87)= 0.19215 which would round to you "0.1922". How do you know "that is not correct"?