After one hour, the distance between them is 16km, so the speed difference between them is 4km/h, that is

Y-x=4, or x-y=4,

From y=2x- 10, solve the equations simultaneously and get:

y= 18，x = 14； Or x=6 and y=2.

So the speed sum of two people is 32 km/h or 8 km/h.