<u>Answer:</u>
-4
<u>Step-by-step explanation:</u>
We are given the following expression which we are to solve:
Since this expression includes brackets as well has plus and minus signs, so we will follow the standard order of operations to solve this expression.
Solving the brackets first to get:
Now adding all the terms up to get:
-4
For this problem you must do Pythagorean theorem:
In this example 10ft is c and 7ft is a (or it could be b, and you'll be solving for a instead of b. It's the same thing, since a and b are both legs)
Plug what you know into the equation:
49 +b^{2} = 100
Bring 49 to the right side by subtracting it:
b^{2} = 51
Now you still must isolate b. The opposite of squaring is taking the square root so take the square root of both sides to cancel it from the left side:
b = 7.1414
b ≈ 7 ft
Hope this helped!