Final answer:
The simplified ratio of ten-dollar bills to twenty-dollar bills Amelia has is 8 to 5, or as a fraction, 8/5.
Step-by-step explanation:
To find the ratio of ten-dollar bills to twenty-dollar bills that Amelia has, we compare the number of each type of bill directly. Amelia has 120 ten-dollar bills and 75 twenty-dollar bills. To simplify this ratio, we can divide both numbers by the greatest common divisor of 120 and 75, which is 15.
120 ÷ 15 = 8
75 ÷ 15 = 5
Therefore, the simplified ratio of ten-dollar bills to twenty-dollar bills is 8:5, which can also be written as the fraction 8/5.