Solve the following system of 3 equations in 3 unknowns.
x - 3z = -5
2x - y + 2z = 16
7x - 3y - 5z = 19

Correct option is B

Given
x - 3z = -5 --- (Equation 1)
2x - y + 2z = 16 --- (Equation 2)
7x - 3y - 5z = 19 --- (Equation 3)
Solution
From Equation 1, x = 3z - 5
Substitute x into Equation 2:
2(3z - 5) - y + 2z = 16
6z - 10 - y + 2z = 16
8z - y = 26 $$\Rightarrow$$​ y = 8z - 26
Substitute x and y into Equation 3:
7(3z - 5) - 3(8z - 26) - 5z = 19
21z - 35 - 24z + 78 - 5z = 19
-8z + 43 = 19
8z = 24 $$\Rightarrow$$​z = 3
Find y by substituting z = 3:
y = 8(3) - 26 = 24 - 26 = -2
Find x by substituting z = 3:
x = 3(3) - 5 = 9 - 5 = 4
Final Answer
So the correct answer is (b) 
Exam Hall Method: