Answer:
its a)the first sequence is geometric bc of the common ratio of 2. the second sequence is arithmetic bc of the common difference of 7.
The last answer is the correct one.
If it does not make sense ask for clarification.
The r% of a quantity x is computed by dividing x in 100 parts, and considering r of such parts. So, the r% of the male is

and similarly, the r% of female is

The number of males decreased by this quantity, so now it is

and the number of female increased by this quantity, so now it is

we know that these two new counts are the same number, so we can build and solve the equality

Subtract 20 and add 0.3r from both sides:

Divide both sides by 0.5 to solve for r:

Let's check the answer
The 20% of 30 is
, while the 20% of 20 is 4. So, we are stating that
which is true because both expressions evaluate to 24.
There are 6, you'd think there would be 8 but the answer is actually 6. A diagonal is a line segment that connects to vertices, the two vertices chosen do not count when forming the triangle, two vertices that are adjacent to that chosen vertex are NOT included when forming the diagonal. It's confusing, but I hope this helps. If you have any follow up questions I'd love to answer them.