Calibrating a Pedometer

I am trying to calibrate a Pedometer which counts the number of steps you take. I'm usng a GPS device to calculate how far I go. Doing both running and walking, I traveled 7600 steps over 7 km. That was a few days ago. Today, I ran 956 steps over 1.1 km and then walked up to 2446 steps at 2.36 km. If my calculations are correct, I take 85 cm per step when walking and 115 cm per step when running.

For those who can solve two variable linear systems, how many steps did I walk on the 7 km segment.

I also did try to calibrate the GPS against the car odometer. It could be understating distances by 4%. It's hard to tell if the car's odometer is incorrect and if the same errors exist at running and walking speeds.