LinearSolve

LinearSolve[m,b] finds an x that solves the matrix equation m.x==b. 

LinearSolve[m] generates a LinearSolveFunction[…] that can be applied repeatedly to different b. 

LinearSolve[a,b] finds an x that solves the array equation a.x==b. 

Please visit the official Wolfram Language Reference for more details and examples on core symbols.