ambrosius, i will start, you finish it . . . for x

a = (495)/(1.0324 - 0.19077log(x - y) + 0.15456(log z)) - 450

(a - 450) = 495/(1.0324 - 0.19077log(x - y) + 0.15456(log z))

(1.0324 - 0.19077log(x - y) + 0.15456(log z)) = 495/(a - 450)

- 0.19077log(x - y) = 495/(a - 450) - 1.0324 - 0.15456(log z)

log(x - y) = [495/(a - 450) - 1.0324 - 0.15456(log z)]/(-0.19077),

you can finish it off . . .