p(x)=x3-19x+30.
We can guess possible zeroes by looking at the factors of 30: 2, 3, 5, 6, 10, 15.
Starting with 2, p(2)=8-38+30=0, so x=2 is a zero. Use synthetic division to reduce to a quadratic:
2 | 1 0 -19 30
1 2 4 -30
1 2 -15 | 0 = x2+2x-15 = (x+5)(x-3).
Therefore the zeroes are c=2, -5, 3.