Basically, for equation 1, you would move the 3y to the other side so that x and y are on the same side. However, because it is a positive, when moving it over, it becomes a negative.
1) x - 3y = -6 2) 2x - 4y = 8
Multiply ALL of equation 1 by 2 so that you could find the value of y.
1) 2(x - 3y = -6)
1) 2x - 6y = -12 2) 2x - 4y = 8
Subtract equations :)
-2y = -20
Divide both sides of the equation by -2, so that y is isolated.
When you think of average speed it would be per hour, so when thinking 30 minutes is .5 of a hour that means when you add 30 minutes and 30 minutes you get 1 hour so you would add 25km and 25km and you would get its average speed per hour, I hope that made sense
