Answer:
Equation B
Step-by-step explanation:
By going through the equations and comparing them to the question, we can determine the correct equation.
Equation A is the multiplication of the distance they have already hiked by 21.
Equation B is the subtraction of the distance already hiked from the total length of the trail.
Equation C is the same as Equation A, but with a factor of 17.5 instead of 21.
Equation D is the addition of the distance already hiked from the total length of the trail.
Therefore, Equation B is the correct answer.
