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>

5b^3 sq rt of a
There's not enough a's
They all 3 have no solution!
Answer:
<DEB= 125 degrees
Step-by-step explanation:
To get this, you would need to know all 2 angles of the triangle.
To find the first angle, simply do 180-107 to get 73(because supplementary angles add up to 180 degrees).
Next, 180-52(given angle)-73 to get 55 because the 3 angles of a triangle add up to 180(triangle angle sum theory).
You would see that <DEB is part of another supplementary angle so, do 180-55 to get 125.
<DEB=125 degrees.