Emily took 300 US dollars to the bank to exchange it for Canadian dollars. The exchange rate on that day was 1.25 Canadian dollars per one US dollar. How many Ganadian dollars did she receive for 300 US dollars?

let x and 400 - x be the two numbers.  

==> 0.80x + 0.85(400 - x) = 400 - 68 from the statement of the problem.  

< ==> 0.80x + 0.85(400 - x) = 400 - 68  

==> 340 - 0.05x = 332  

< ==> -0.05x = -8 ==> x = 160, the first number ==> 400 - x = 240, the second number.

so part 1: the y values stay the same, but the x values are opposite signs.

part 2 & 3: the line will be of equal lengths and will be straight.

part 4: you'd see the same characteristic because the x coordinate becomes a negative making them at equal distances from the y axis?