I need help i dont know where they go thx

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

Adam plans to choose a video game from the section of the store where everything is 75% off. he writes the expression d-0.75d to find the sale price of the game if the original price is d dollars. gena correctly writes another expression, 0.25d, that will also find the sale price of the game if the original price is d dollars. use the drop down menus to explain each part of adams and rena's expression

On average, how many more hits will he get when he bats 100 times at home during the day as opposed to 100 times away at night?