Its solving a 3 by 3 system of equation

Question

4a+7b     =5
8a     -3c=36

      6b-3c=6

Answer 1

1)  4a + 7b  = 5

2)  8a - 3c = 36

3)  6b - 3c = 6

subtract eq(3) from eq(2):

8a - 3c = 36

6b - 3c = 6

__________

8a - 6b = 30  (a)

multiply eq(1) by 2, subtract from eq(a):

8a - 6b = 30

8a + 14b = 10

_____________

          -20b = 20

b = -1

using eq(1):

4a + 7(-1) = 5

4a = 12

a = 12/4 = 3

using eq(2):

8(3) - 3c = 36

-3c = 12

c = -12/3 = -4

 

a = 3, b = -1, c = -4

You can check these by plugging the values into eqs 1 - 3