Which expression best represents the difference between triple a number and double a number?

For how answer my question this will be the last question can you answer in math subject

Write an equation in slope intercept form of the line passes through the given point and is parallel to the graph of the given equation (0,0); y=3/8 x+2

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?