4.5x + 6y = 12
Subtract 4.5x to both sides:
6y = -4.5x + 12
Divide 6 to both sides:
y = -3/4x + 2
Plug in -3/4x + 2 for 'y' in the first equation:
3x + 4y = 8
3x + 4(-3/4x + 2) = 8
Distribute 4:
3x + -3x + 8 = 8
Subtract 8 to both sides:
3x + -3x = 0
Add 3x to both sides:
3x = 3x
Therefore there are infinitely many solutions.