Answer:
A - Since Elena biked for 8 miles on Saturday, 100% of her distance traveled was 8 miles.
B - Now, on Sunday she traveled 75% of what she traveled on Saturday, which arises from the following calculation:
8 x 0.75 = X
6 = X
So on Sunday she traveled 6 miles.
C - Finally, on Monday she traveled 125% of what she traveled on Saturday, which arises from the following calculation:
8 x 1.25 = X
10 = X
So on Monday she traveled 10 miles.