if N=13xy45z,and 792|N, then N=

hint: 792=8*9*11

but the number 13xy45z has a straight line above it. What does that mean ?

Do you mean a repeating symbol like this? It means the numbers repeat. For example:

\(\frac{1}{7}=0.\overline{142857}=0.142857142857142857142857...\)

yup. but is it possible for a non decimal number to have that symbol ?

It would not make sense to have that. If there is, post it.