What is the answer to this??? please I need to know!

Which values for a and b will create infinitely many solutions for this system of equations? ax-y=8 2x+y=b

What other information do you need to prove triangle dac=bca by asa

Kayla has a $500 budget for the school party. she paid $150 for the decorations. food will cost $5.50 per student. what inequality represents the number of students, s, that can attend the party?