just kidding in need help with (-2)^-13x(-2)^5

Using the property     a^m * a^n  =  a^(m + n) we have that

(-2)^-13 * (-2)^5  =   (-2)^(-13 + 5)   =  (-2)^(-8)  =  1 / (-2)^8  =  1 / 256