Hope you guys can help me out I would really appreciate the help!!

Why do interests rates on loans to be lower in a weak economy than in a strong one

In the polynomial below, what number should replace the question mark to produce a difference of squares? x2 + ? x - 36

Acar started driving from city a to city b, distance between which is 620 miles, at a rate of 60 mph. two hours later a truck left city b and started moving towards city a at a rate of 40 mph. what distance from city a is the point where the truck and the car will meet?