5x(x + 2/3) + (x + 2/3) = 0
5x^2 + 10x/3 + x + 2/3 = 0
Multiply each term by 3 to clear the fraction
15x^2 + 10x + 3x + 2 = 0
15x^2 + 13x + 2 = 0
Factor the trinomial
(3x + 2)(5x + 1) = 0
Set each factor equal to zero and solve
3x + 2 = 0
3x = -2
x = -2/3
5x + 1 = 0
5x = -1
x = -1/5