2a+c=10 , a+2b=-10, b+2c=5 then what is the value of a b c

Question

Solve this equations so easy but i am so irritating this equations....

Answer 1

Substitute the 2nd equation into the 1st equation. keep the last equation.  From eq2,

 

a = -2b - 10

 

2(-2b - 10) + c = 10

-4b - 20 + c = 10

 

-4b + c = 30                         eq1

 

b + 2c = 5                             eq3

 

 

Substitute eq3 into eq1.

 

-4(-2c + 5) + c = 30

 

8c - 20 + c = 30

 

 

Solve for c from this equation.

 

9c = 50

 

c = 50/9

 

 

Plug in this value of c into eq3 to find b.

Then use the value b into eq1 to find a.