Answer:
266.6 per year
Step-by-step explanation:
53392 / 20 = 266.6
= 266.6 per year
7 is the number increased by 5 = 12
The expression 36x² - 121 is in the 'difference of two squares form' which is (a² - b²)
Factorising (a² - b²) gives (a+b)(a-b)
Factorising 36x² - 121 gives (6x+11)(6x-11)

From there we can see that because x equals both to a and b, it must be that a = b.