The function f(x) = 5/9 (x − 32) can be used to determine the temperature in °C when the temperature is x°F. Find the inverse function that can be used to determine the temperature in °F when the temperature is x°C. The function that can determine the temperature in °F is f−1(x) = ?

the arc length is found by finding the circumference of the full circle (2xpixradius) and then dividing by 4 to find just one quarter of the circle (90 degrees).

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.