A deep-sea diver must descend and ascend in short steps to equalize pressure on his body. If the diver rises toward the surface
too fast, he may suffer from a physical condition called "the bends." Suppose the diver started at 82 feet below the surface and rose in 5 steps of 15 feet each. Use an integer to describe his new position in relation to the water surface.
The total distance the diver rose is 5*15 = 75 feet
If we take the zero at the water surface, then the initial position, that is, 82 feet below the surface has to be considered as -82. The 75 feet risen by the diver is a positive quantity, then his new position, in relation to the water surface, is -82 + 75 = -7 feet, i. e. 7 feet below the surface.
Start by multiplying 15 by 5, and you get 75. then subtract that from 82, and you get 7. Since you are below the surface, the number is negative. So you get -7.
