Use the given information to write the standard form of a hyperbole:
Focus (-3, -26)
Vertex (-3, -18)
I assume you know the standard form of a hyperbola. and what a, b, and c mean. You can gather the information for the three and form the equation. First things first, you know that c = 29 because it is shifted 29 units away from the center. You know that a is 21 because the vertex is 21 units away from the center. With the relationship c^2 = a^2 + b^2 in mind for hyperbolas, you can solve for b. Since it is clear that the major axis is parallel to the y-axis since the change for the vertex is of the y-value, you know that in the hyperbola equation, it will be y^2 / a^2 - x^2 / b^2 = 1. You have and b, so fill and you have your formula.