So to begin your problem, you know that your car already has an average which is 65km/45 mins. The problem wants you to change this to km/hr. This means that you need to convert minutes to hours. A simple way to do this is by using fractions. Set your problem up with fractions similar to this: 65km/45 mins x 60 mins/1 hr. the whole point is to cancel out your minutes, and leave the hours as your new unit for the denominator 65km/45 x 60/1 hr. now you want to reduce (I divided the first fraction by 5) 13km/9 x 60/1 hr. 780km/9hrs. That would be your answer. If someone can double check my math that would be fantastic.
65km in 45 min 1 hour=1h=60min 45/60=3/4 65km=3/4hour multiply both sides by 4/3 to clear fraction 260/3=1 hour 86 2/3 =1 hour aprox 86.666666666 km per hour
first you set up the problem, supplementary angles equal 180 degrees so the equation should look like, 4x+x+15=180. then you solve from there by combining like terms and you should get x equal to 33
