Answer:
75 chairs
Step-by-step explanation:
1. 9x+3 : write equation
2. 7x+19 : write equation
3. 9x+3=7x+19 : make both equations equal to each other
4. 2x+3=19 : subtract 7x from both sides
5. 2x=16 : subtract 3 from both sides
6. 8 : divide 2 on both sides of the equal sign
7. 9(8)+3=75 : plug 8 into the equation