Answer:
7 juniors and 2 coins
Explanation:
25% is equal to 25/100 which is 1/4. To find 1/4 of 28 it would be 28/4 which is 7. There are 7 juniors in the program.
5-cent: x
10-cent: y
25-cent: z
5x+10y+25z=320 which is also x+2y=5z=64. You can subsitute y for x+3 because he has 3 more 10-cent than 5-cent. x+x+3+z=23 which is 2x+z=20=z=20-2x.
Substitute
x+2(x+3)+5(20-2x)=64
x+2x+6+100-10x=64
7x=106-64
7x=42
x=6, z=20-2*6=8, z-x=8-6=2