) 2x_(1)+x_(2)+x_(3)&-2 4x_(1)+3x_(2)+3x_(3)&+x_(4)-3 8x_(1)+7x_(2)+9x_(3)+5x_(4)&=1 6x_(1)+7x_(2)+9

The correct answer is: This is a system of linear equations with four variables , , , and . The system can be solved using methods such as substitution, elimination, or matrix operations.