Answer: 
Step-by-step explanation:
Some transformations for a function f(x) are shown below:
If 
, the function is translated up "k" units.
If 
, the function is translated down "k" units.
If 
, the function is reflected across the x-axis.
If 
, the function is reflected across the y-axis.
Therefore, knowing those transformations and given the exponential parent function:
If it is reflected across the y-axis and the it is translated down 4 units, we can determine that the resulting function is:
X = velocity of plane
y = velocity of wind
x - y = 1680/5 = 336 mph .....(1) [ plane flying against the wind]
&
x + y = 1680/4 = 420 mph....(2) [ plane flying with the wind]
Adding (1) and (2) to eliminate y gives
2x = 756
x = 378 mph is the speed of the plane with no wind.
X = pencils, y = pens
8x + 6y = 8.50
4x + 4y = 5.....multiply by -2
----------------
8x + 6y = 8.50
-8x - 8y = -10 (result of multiplying by -2)
-----------------add
-2y = - 1.50
y = -1.50 / -2
y = 0.75 <=== pens cost 0.75
4x + 4y = 5
4x + 4(0.75) = 5
4x + 3 = 5
4x = 5 - 3
4x = 2
x = 2/4
x = 0.50 <== pencils cost 0.50
What is the rule? Then i will know how to it
