13 + x/2 = 3x Common denominator is 2.
2(13 + x/2) = 2 * 3x Distributing the 2 through the parenthesis
2 * 13 + 2x/2 = 2 * 3x
2 * 13 + x = 2 * 3x
26 + x = 2 * 3x
26 + x = 6x Subtract the x
26 = 6x - x
26 = 5x Divide by 5
26/5 = x
So x = 26/5 which can be simplified to x = 5 1/5.