Hello,
Adding the 2 equations,
x+y+x-y=k+k ==>2x=2k==>x=k
if x=k, y=k-k=0
solution is (k,0)
Answer:
The difference between 19 and 8 is 11.
Step-by-step explanation:
Given:
The difference between a number and 8 is 11
Find the number.
Solution:
Let the unknown number be 
The difference between the unknown number can be written as:

We are given that the difference =11
So we can write the equation to find
as :

Using additive property to solve for 
Adding 8 to both sides to isolate
on one side.

∴ 
∴ The unknown number = 19
Stan's, Mark's and Wayne's ages are 35 , 36 and 37 years respectively.
<em><u>Explanation</u></em>
Stan's, Mark's and Wayne's ages are <u>consecutive whole numbers</u> and Stan is the youngest and Wayne is the oldest.
So, lets assume that Stan's, Mark's and Wayne's ages are
and 
Given that, the sum of their ages is 108. So, the equation will be.....

So, Stan's age is 35 years , Mark's age is (35+1)= 36 years and Wayne's age is (35+2)= 37 years.
Let's assume two variables x and y which represent the local and international calls respectively.
x + y = 852 = total number of minutes which were consumed by the company (equation 1)
0.06*x+ 0.15 y =69.84 = total price which was charged for the phone calls (Equation 2)
from equation 1:-
x=852 -y (sub in equation 2)
0.06 (852 - y) + 0.15 y =69.84
51.12 -0.06 y +0.15 y =69.84 (subtracting both sides by 51.12)
0.09 y =18.74
y= 208 minutes = international minutes (sub in 1)
208+x=852 (By subtracting both sides by 208)
x = 852-208 = 644 minutes = local minutes