1. If x + y = 13 and 2 x - y = 2, then x - y is equal to   13   0   -3   3   -11   Hint Half-n-half Clue   2. A university has 5000 graduate students. The number of undergraduate students is 5  / 4  times the number of graduate students. What fraction of the students in the university are undergraduates?   5 / 9   9 / 4   5 / 4   4 / 9   9 / 5   Half-n-half Clue   3. If 5 x + 3 y = 21 then 30 x + 18 y is equal to   126   21   none of these   147   168   Half-n-half Clue   4. A piece of equipment consumes c cents per hour of fuel and requires d dollars per hour for other operational costs. What is the cost in dollars of operating the equipment for 600  hours?   600 c + 6 d   6 c + 600 d   6 (c + d)   600 (c + d)   0.01 c + d   Half-n-half Clue