<span> x(4-k)=p
[x(4-k)=p]/x
4-k=p/x
-4 = -4
-k=p/x-4
k=4-p/x
</span>
Answer:
7
Step-by-step explanation:
The expression is (15+6) */* 3. This is because we add up all the costs to get the total, and divide the total by three because there are three friends splitting the cost.
The first step for solving this problem is to multiply both sides of the bottom equation by -3.

Add the two equations together.
6x - 9y - 6x + 9y = 16 - 21
Eliminate the opposites.
-9y + 9y = 16 - 21
Remember that the sum of two opposites equals 0,, so the equation becomes the following:
0 = 16 - 21
Calculate the difference on the right side of the equation.
0 = -5
This means that the statement

is false for any value of x and y. That means that the answer to your question is (x,y) ∈ ∅,, or no solution.
Let me know if you have any further questions.
:)