The linear equation with one solution. Examples: x+2 = 3, 5x = 10, 2x+1 = 5. The linear equation with infinite solutions. Examples: x = x, x+2 = x+2, 2(x+3) = 2x+6. The linear equation with zero solutions. Examples: x = x+2, x+2 = x+3, 2(x+1) = 2x+3.