Let the Jaguar travel for x hours to catch the truck.
Because the Jaguar begins to chase the truck after a half hour, the truck traveled for (x + 0.5) hours.
The distance the Jaguar traveled is
d₁ = (55 mph)*(x h) = 55x mi.
The distance the truck traveled is
d₂ = (50 mph)*(x + 0.5) = 50x + 25 mi
The two distances are equal, therefore
55x = 50x + 25
5x = 25
x = 5 hours
The Ford truck traveled for x+0.5 = 5.5 hours.
Answer: 5.5 hours