Car A is 500metres behind car B.Car A is travelling at 130km/h and car B at 80km/h

How long does it take for car A to catch car B.

Initially I make the unknown time = T

I assume A(130/h)* T =B(80/h)-0.5

Am I thinking in the right direction?

Oh hang on.The difference in speed=50km/h so maybe

speed A-speed B * T=0.5

(150k/h-80k/h)*T=0.5

50k/h*T=0.5

T=0.5/50

T=0.01 hours=36 seconds.

That seemed messy.What is the best way?