Answer:
3x + 9 + 4x + x simplifies to 8x + 9
y = mx + b: m is slope, b is y-intercept
no solutions: 8x + 8
(no solution from the same slope and different y-intercept)
one solution: 4x + 1
(different slope needed)
infinitely many: 8x + 9
(same y-intercept, same slope_