In Exponential Functions, with the Y=ab^x, how do you know when to subtract to find b or when to add

Abcd is a parallelogram find the valuse of x

What are the soultion(s) to the quadratic equation 40- x^2=0

You're locked out of your house. the only open window is on the second floor, 25 feet above the ground. there are bushes along the edge of the house, so you will need to place the ladder 10 feet from the house. what length ladder do you need to reach the window?