Answer:
x = 6
Step-by-step explanation:
The way to solve this is by subtracting 2x from both sides. Now we have
2x-5=7
Then we add 5 from both sides. Now we have
2x=12
We do this because we want X by itself
Then we divide by 2 on both sides and now we have
x = 6
If you have any questions feel free to ask in the comments.
Answer:
Let f_n be the number of rabbit pairs at the beginning of each month. We start with one pair, that is f_1 = 1. After one month the rabbits still do not produce a new pair, which means f_2 = 1. After two months a new born pair appears, that is f_3 = 2, and so on. Let now n 
3 be any natural number. We have that f_n is equal to the previous amount of pairs f_n-1 plus the amount of new born pairs. The last amount is f_n-2, since any two month younger pair produced its first baby pair. Finally we have
f_1 = f_2 = 1,f_n = f_n-1 + f_n-2 for any natural n 3.
