Is the question wrong? Why do ternary equations have four groups of equations?

According to the first three groups of solutions

( 1)+(2): 5x 1-2x3=3 (4)

(2)+(3) De: 7x 1-4x3=3 (5)

(4)*2-(5): 3x 1=3，x 1= 1。

Substitute x 1= 1 into (4) to get the result: x3= 1.

Substituting x 1= 1 and x3= 1 (1) gives the result: x2=2.

Empirical calculation, fortunately, the fourth group also has this solution.