library(matlib)

1 −1 4 1 2 0 −1 −1.5 −1 1 0 2

A <- matrix(c(0, -2, -1, 2, 3, 2, 3, -2, 3), nrow = 3, ncol = 3)
b <- c(6, -1, 2)
A
##      [,1] [,2] [,3]
## [1,]    0    2    3
## [2,]   -2    3   -2
## [3,]   -1    2    3
b
## [1]  6 -1  2
Solve(A, b)
## x1      =           4 
##   x2    =  2.53846154 
##     x3  =  0.30769231