1. get rid of your parenthesis
2. in order to do so you must look inside of the parenthesis and check if you have any like terms if so combine them
3. next use the distribution property or otherwise known as the rainbow
4. if you have an exponent to the right of your parenthesis then use the exponent rule
5. combine like terms by adding coefficients
6. finally combine the constants
To solve this, you can set up an equation. Make the length of the shortest side x, so the 2 sides double the length will equal 2x. Since they all equal the perimeter of 36, do x + 2x + 2x =36. These values all represent the sides(2 longer, one short). Combine like terms to get 5x=36 then divide by 5 to find the value of x. x=7.2in meaning the shorter side is 7.2 inches while the longer sides are both 14.4 inches each since they are double in size.
4. 8+12=20
4 (2+3)
First you add 2+3 and get 5
Next, since the 5 is now in the parentheses, it indicates that you have to multiply
Finally, 5 times 4=20
B. (k+10f)(k-5f) you can tell in 2 ways. 1. if the second sign is neg then the signs in the factors are going to be one neg and one positive so that knocks out C and D. Then you look at the second term and since the 5 is positive then the 10 has to be positive so you end up with a positive 5kf.
The second way is to FOIL them out. When you check B you get

combine your like terms and you have your original expression of

Hope that helps