25 quarters because if you set up a system of equations you get x+y=30 since there are x number of half dollars and y number of quarters plus each other is 30. Next equation is .5x+.25y=8.75 half dollar is 50cents while a quarter equals 25 cents and together they have to equal 8.75. Now you eliminate one variable then you add the remaining variable and the amounts together then you divide if you eliminated the x variable your answer is the one you get after you divide. If you eliminate the y variable then you have to plug it then you get your answer. hope this helped
