This is the same as finding the two solutions to the equation z2 = 7 - 24i.
Here are the steps. When you have read them, I recommend trying them yourself and then ask questions if you are still having trouble with this problem.
1) Write 7 -24i in trigonometric form. (This looks like r(cos θ + i sin θ) and is shortened to r cis θ by some people.)
2) Set up the formula for the two square roots in trigonometric form. They have the form
wk = √r cis ((θ + 360°k)/2) for k = 1 and k = 2 (assuming degrees for the angles)
3) Plug in k = 1 and k = 2 into this formula and simplify the angle(s).
4) Evaluate and rewrite in standard form (a + bi) if that is required.
If you need any help with any of these steps, please send a reply as quickly as you can so you can get the problem done.