Final answer:
Tre ran 34 miles on the first day. This is determined by setting up an equation where Tre's first day mileage plus the 23 miles he ran the second day equals the total mileage of 57 miles, and then solving for the unknown.
Step-by-step explanation:
To find out how many miles Tre ran on the first day, we can set up an equation where x represents the unknown number of miles run on the first day. Since we know that Tre ran a total of 57 miles over two days, and that he ran 23 miles on the second day, the equation looks like this:
x + 23 = 57
To solve for x, we subtract 23 from both sides of the equation:
x = 57 - 23
x = 34
Therefore, Tre ran 34 miles on the first day.