83, 89, and 97 are three primes between 80 and 100.
The primes between 30 and 50 are 31, 37, 41, 43, and 47, all of which are odd. All other numbers between 30 and 50 are composite.
To mentally find 2*50*25, you could either first multiply 25 by 2, to get 50*50, which can easily be calculated as 2500, or you could multiply the 50 by 2, for a result of 100*25, which is clearly also 2500.
My estimated answer for 1 is x=1.59 or x=-1.26 and my exact answer is (in word form) x= 1 plus or minus the square root of 73 over 6. my estimated answer for 2 is x=-0.34 or x=1.74 and my exact answer (in word form) is x= -7 plus or minus the square root of 109 over -10. I took a picture of my work and hopefully you can read it
Oh wait a minute i have to write this down
If it was one year it would be 2200 and you just keep adding 200 for each year.