How to solve it and get the answer

X + 2y + 3z = 73(1)
3x + 2y + 10z = 195(2)
-x - y - z = -31(3)
You can solve these by elimination:-
First   add equations (1) and (3) to eliminate x:-
y  + 2z = 42(4)
Now multiply equation  (1) by -3:-
-3x - 6y - 9z = -219    Now add this to equation (2) this gives:-
-4y  + z = -24(5)
multiply this by -2:-
8y - 2z = 48(6)   Now add this to equation 4 to eliminate z:-
9y = 90 
y = 10 

and from equation 4:-
10 + 2z = 42
2z = 32
z = 16  

Now to find  value of x plug in y = 10 and z = 16 into equation (1):-

x + 2(10 + 3(16) = 73 giving x =  73 - 20 - 48 = 5
 
Answer is  x = 5, y = 10 and z = 16