Solving simultaneous equations with R

Question

Suppose I have the following equations:

 x + 2y + 3z = 20  
2x + 5y + 9z = 100  
5x + 7y + 8z = 200

How do I solve these equations for

Answer 1

A <- matrix(data=c(1, 2, 3, 2, 5, 9, 5, 7, 8),nrow=3,ncol=3,byrow=TRUE)    
b <- matrix(data=c(20, 100, 200),nrow=3,ncol=1,byrow=FALSE)
solve(A)%*% b

Note that this is a square matrix!