135. Solving a chemistry problem

12. V-1. To build a calibration graph for the determination of nickel in bronze, the following results were obtained:
W(Ni),% 3.00 3.42 3.84 4.24
∆S 0.58 0.662 0.740 0.821
for two steps of the line Sn ∆Sbase=0.828. When photometrically measuring the spectrum of bronze samples photographed on another plate, ∆Sb was obtained for two steps of the same line Sn, and for the analytical pair Ni-Sn in the spectrum of the sample on the same plate Sx´. Determine the mass fraction of tin in the samples:
Sample 1
∆S t 0.765
∆Sx 0.566