Write the inverse of this relation.

{ (1, -3), (-2, 3), (5, 1), (6, 4) }

Your coordinates would be : (-3,1), (3,-2), (1,5), and (4,6).

All you need to do is to flip around the x and y values of each coordinate.

So, just follow this: (x,y) ---> (y,x)

(1,-3) ---> (-3,1)

(-2,3) ---> (3,-2)

(5,1) ---> (1,5)

(6,4) ---> (4,6)

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.