7x + 7y = 8x - 8y 8x - 7x = 7y + 8y x = 15y
Plug into first eq:
7(15y) + 7y = 5432 105y + 7y = 5432 112y = 5432 y = 48.5And then you'd continue from here to get the speed of the aircraft in still air.
The key is that the two original equations are equal to the same constant. When I put them together to get rid of that constant in the first line of this solution, I was in effect doing the adding and subtracting of the two lines of the previous solution in one fell swoop.
So, then my question is, WHY THE HELL DOES THE SCHOOL CURRICULUM TEACH KIDS HOW TO DO THINGS THE STUPID WAY?!?!?!?!
Particularly when it really doesn't make any sense. It's not easier to understand and it requires a leap of faith that it will work out. In my solution, you can actually see what's going on with the x's and y's and all the laws of Math symbols are preserved.