.
Infinitely many.
Since the two equations are dependent, including their right sides.
The two equations are equivalent and, therefore, they represent one/(the same) straight line.
See the lesson
- Geometric interpretation of a linear system of two equations in two unknowns
in this site.
Also, you have this free of charge online textbook in ALGEBRA-I in this site
- ALGEBRA-I - YOUR ONLINE TEXTBOOK.
The referred lesson is the part of this online textbook under the topic "Systems of two linear equations in two unknowns".