## Algebra: A Combined Approach (4th Edition)

a. $x + y = 4$ and $x + y = 3$ are parallel lines. Both linear equations are in the standard form ($Ax+By=C$). Their slopes are calculated as $m=-\frac{A}{B}=-\frac{1}{1}=-1$. Since they have the same slope, they are parallel lines. b. Since, they do not intersect, the system does not have a solution.