It will take Nayeli 4 days
I got this answer by dividing 50÷1/4 which equals 12.5. If Nayeli plans to swim 1/4 mile each day until she has reached 50 miles, she would've done 12.5 miles per day. To check if I am correct, multiply 12.5×4 and it will equal to 50. (also, I did 25÷2 to get 12.5. The reason I did this is because 25 is half of 50, so to split it into 4 I had to make 25 half of what it already is)