Answer
one solution
Work Step by Step
Say that the unknowns were x, y, and z.
The third row represents the equation
$z=5.$
Back-substituting into the second row, we find a unique $y$.
$y+2(5)=13$
$y=3$
Back-substituting into the first row, we find a unique $x.$
$x+(3)+2(5)=19$
$x=6$
Solution set: $\{(6,3,5)\}$
The system has one solution.