Question

Please explain...................

Answer 1

You basically have a system of 3 equations with 3 unknowns.
5x/3 + y = c;
2y = c - 4x;
x + y = 6;
Substitute say the third equation into the second one.

2(6-x)=c-4x
Solving this for x gives you:
x=c/2 - 6

Now we can substitute the third equation onto the first one:
5x/3 + (6-x) = c
And now substitute for x= c/2 - 6 to get an equation which is only in terms of c. Therefore you can get the value of it form there.

Answer 2

2y = c - 4x
4x + 2y = c (1)


5x/3  + y = c
5x + 3y = 3c
(5x+3y)/3 = c (2)

from (1) and (2):
4x + 2y = (5x + 3y)/3
12x + 6y = 5x + 3y
7x = -3y

x + y = 6 so x = 6 - y
 

substitute x = 6 - y into 7x = -3y

7x = -3y

7(6 - y) = -3y

42 - 7y = -3y

42 = 4y 

y = 10.5

x = 6 – 10.5 = 6 – 10.5 = -4.5

 

Now you know x = -4.5 and y = 10.5 you can find the value of C

c = 4x + 2y 

c = 4(-4.5) + 2(10.5) 

c = -18 + 21

c = 3