Answer:
The shaded area is 
Step-by-step explanation:
we know that
The shaded area is equal to the area of the large square minus the area of the two smaller squares
so

Calculate the shaded area
Remember that

substitute

Y - 23 = - 6 ( x + 2 )
Y - 23 = - 6x - 12
Y = - 6x + 11
Y + 6x = 11
Thanks me if it is correct !!
Answer:
Any letter you want
Step-by-step explanation:
The letters used for variables don't matter. What matters is what the variables represent: their numerical value. Variables are just to help identify what needs solving. Other common variables are a, b, and c which are found frequently in trigonometry. To answer your question, there are no "next letters." You can use any letter you'd like as a variable because it holds the same numerical value. Basically, the whole alphabet is at your disposal.