(i) Coefficient of x in 13x is 13.
(ii) Coefficient of y in -5y is -5.
(iii) Coefficient of a in 6ab is 6b.
(iv) Coefficient of z in -7xz is -7x.
(v) Coefficient of p in -2pqr is -2qr.
(vi) Coefficient of y2 in 8xy2z is 8xz.
(vii) Coefficient of x3 in x3 is 1.
(viii) Coefficient of x2 in -x2 is -1.