Hey there! :)
~ They give us some good information in this equation. Let's use it! This can be used to change "45 min" into ".75 hours".
~ Now, let's write an equation; "distance = speed * time."
~ 3(.75) + .5x = 6
~ 2.25 + .5x = 6
~ .5x = 6 - 2.25
~ .5x = 3.75
~ x = 3.75/.5
~ x = 7.5 km/hr