A vector perpendicular to both the vectors 2i^-j^+5k^ and X-axis is
j^+5j^
j^-5k^
5j^+k^
i^+j^+k^
Cross product of two perpendicular vector should be zero.
i^j^k^2-15100=-(0-5)j^+(1)k^=5j^+k^
The vector perpendicular to both vectors is 5j^+k^