20 Answer: a₁ = 4
<u>Step-by-step explanation:</u>

21 Answer: n = 13
<u>Step-by-step explanation:</u>

22 Answer: n = 5
<u>Step-by-step explanation:</u>

The equation for surface area on a cube is 6 * L^2, where L is side length. Essentially, six squares of equal size
12^2=144
6 * 144=864
I hope you found this both helpful and explanatory
1st step is to put the numbers from smallest to biggest. Once you do that cross one out on the left, then the right, then the left, then the right and so on. Sometimes there will be 2 numbers left, so you add them up and subtract by two. If you need further help ask! :)
Answer:
7.9982
Step-by-step explanation:
-The function for an earthquake's magnitude is given by R = 0.67log(0.37E) + 1.46
-E is energy in kwh.
#For 15,500,000,000 kilowatt hours the magnitude would be:

Hence, the earthquakes magnitude is 7.9982