I don't understand plz help out

Name each raycalculation tip: in ray "ab", a is the endpoint of the ray.

Which values of p and q result in an equation with exactly one solution? px-43=-42x+q choose all answers that apply: a) p=-43 and q=-43 b) p=42 and q=43 c) p=43 and q=−42 d) p=42 and q=42

Using only the digits 5, 6, 7, 8, how many different three digit numbers can be formed if no digit is repeated in a number?