The curve on the graph represents the distance of individual with time. The time is mentiond on x axis and distance on y axis.
For first part d(2) is to be calculated means distance at t=2.
So from the curve at t=2 the corresponding distance is 4 miles. So d(2)=4.
For second part d(2.75) is to be calculated means distance at t=2.75. From the curve it can be observed that distance between t=2 to t=3 is constant and equal to 4. So d(2.75)=4.
For the third part, d(5) means distance t=5, from the curve it can be observed that at t=5 the distance lie in midway of 5 and 6. So d(5)=5.5.
For the fourth part, d(10) means that distance at t=10. From the curve it can be observed that at t=10, the distance is 0. So d(10)=0.