What is A correct interpretation of the expression 2-(-7)

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?

The constitution gives congress the power to create federal courts lower than the supreme court higher than the supreme court equal to the supreme court, unaffected by the supreme court.

Acertain volume of water contains 100000 hydrogen atoms and 50,000 oxygen atoms how many hydrogen atoms are in a volume of water containing 4 million oxygen atoms