A=[1,15;1,20];
b=[362.78;517.35];
n=length(b);
 
 for k=1:n-1
   for i=k+1:n
     factor =A(i,k)/A(k,k);
     A(i,k:n)=A(i,k:n)-factor*A(k,k:n);
     b(i)=b(i)-factor * b(k);
   end
 end
 
 x=zeros(n,1);
 for i=n:-1:1
   x(i)=(b(i) - A(i,i+1:n)*x(i+1:n))/A(i,i);
 end
 
z= x(1) + 16*x(2);
disp(z);