Determine if the three numbers can be the side lengths of a triangle

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

Write two subtraction equations that are equivalent to 5 + 12 = 17.

Nicole purchased a container of cashews that weighs 5 kilograms. zion purchased a container of cashews that weighs 4,900 grams. how many more grams of cashews did nicole purchase?