It seems your equation is:
(4P + 3Q - 4R) / (P - R) = 19
(4P - 4R) + 3Q = 19(P - R)
3Q = 15(P - R)
Q = 5(P - R)
5S - Q = 0, where S = P - R
from (5S - Q = 0),
S = t
Q = 5t
from (S = P - R = t)
P = k + t
R = k
A final Solution is: P = k + t, Q = 5t, R = k, k,t > 1