Casey likes to run. she runs an additional 1/4 mile each day. on the last day, she ran 1 1/4 miles. if she ran 1/2 mile her first day, for how many days has she been running?

Three days,
1 1/4 = 5/4  
1/2= 2/4
2/4+1/4= 3/4 the first day
5/4-3/4= 2/4 
2/4 = 1/4 and 1/4 = two days
the first day+ two days= 3 days

She ran for 3 days because 1/2 is equal to 2/4 and if she adds 1/4 every day until 1 1/4 that's 3 days.
Hope this helps!!!
Brainleist???

No a triangle cannot be formed because when you add the two smallest number together (which would be 11) the have to be bigger than the number it is "against" ( which would be 12)