Sequences And Series

For three positive integers p, q, r, \({x^{p{q^2}}} = {y^{qr}} = {z^{{p^2}r}}\) and r = pq + 1 such that 3, 3 log\(_yx\), 3 log\(_zy\), 7 log\(_xz\) are in A.P. with common difference \(\frac{1}{2}\). Then r-p-q is equal to