It's either 1050 or 1.050 if that was suppose to be a decimal or a comma after the eight
notice, the denominator for each fraction is the same, thus the LCD is just 3.
Letter c because if u multiply 5•3 you get 15
5/7=15/21 and 2/3=14/21, So Leah ran 1/21 of a lap further
The property being used is the Additive Identity Property.
I hope I helped! :D