Question

kristen can run 9km/h and walk 3km/h. she completed a 42km marathon in 6 hours. what distance did kristen run during the marathon?

Answer 1

Let
x = distance traveled running.
y = distance traveled walking.
x + y = 42
1 / 9x + 1 / 3y = 6
Solving the system of equations:
-3 * (1 / 9x + 1 / 3y) = - 3 * (6)
-1 / 3x + -y = -18
Then,
x + y = 42
-1 / 3x + -y = -18
Adding up:
-1 / 3x + x = 24
2 / 3x = 24
x = (3/2) * 24
x = 36 Km
Answer:
kristen ran 36 Km during the marathon