Use the substitution y = 3x + 1 to solve for x :

5(3x + 1)² + 6(3x + 1) - 8 = 0.

Find the values of x if p + 7 = 0, q - 12 = 0 and x² + px + q = 0.

If x = p is a solution of the equation x(2x + 5) = 3, then find the values of p.