Ajogger runs 5.0 km on a straight trail

Good for him !  If he's also adhering to a healthy diet, getting plenty of sleep, avoiding substance dependence, and minimizing his stress level, then he's doing everything he can to maximize his chances for a long, healthy, pleasant and rewarding fun life.  

carla slowed down in the beginning of her trip, stopped, and then sped up

see the picture for the vector

the magnitude of the vector by pythagorean theorem

r = √( (-10)^2 + (3)^2 ) = √109

magnitude = √109 units

the direction angle between vector and x-axis is

tan^(-1)(3/10) = 16.699

so the direction is approximately 16.7 degrees north of west