A 5ft by 5ft square is nailed in the bottom left corner. 3 100 pound forces are applied to the other 3 corners
the force applied to the upper right corner is at a 40 degree angle

What equations would be used to answer the questions below? I keep finding equations but Im not sure what all the signs and letters mean and how they apply.

What is the torque on the nail?( ft pounds)
net horizontal force on the nail?(in pounds)
net vertical force on the nail? (in pounds)
magnitude of resultant force on nail?( in pounds)

If you start working this out yourself and let us know where you are getting stuck someone will help you along to the next step but this site will not do your homework for you, it's in the terms of use.

To help get you started, draw a diagram of this problem, and determine the components of each force in the x and y directions. Once you do that you can sum all 3 x-direction forces to get your answer to question 2, and then sum all the y-direction forces for question 3. The torque that each force applies to the nail is the force in the x direction times its vertical distance from the nail plus the force in the y direction times its horizontal distance from the nail - but be sure to get the signs right (clockwise torques are positive and counter-clockwise torques are negative). Add all the torques up to get your answer to question 1. To answer #4, use Pythagorean theorem on the X-direction and Y-direction forces that you found in answering questions 2 and 3 to figure out the resultant magnitude of total force.

If you could give us a diagram it may help.

Or perhaps you can re-read the question and perhaps find more details.

That is a statics question.

First convert each force into a cartesian vector. Then resolve them into their components. If everything is in equilibrium you can use:

use "Sigma" Fx=0
Sigma Fy=0
Sigma Fz=0