3. Let a taco's cost be t and the cost of a glass of milk be m:t + m = 2.1, 2t + 3m = 5.15. This is choice D.
4. The only difference is that 4 has been added to the y-value, so the graph remains congruent, but it is moved up along the y-axis, which is choice H.
5. The total number of sandwiches sold is 500, so the fraction of ham-and-cheese sandwiches is 75/500 = 3/20. Since an entire circle is 360 degrees, the fraction for the ham-and-cheese sandwiches is (3/20)(360) = 54 degrees, which is choice C.