Percent decrease : (original number - new number) / original number..*100
= (225,000 - 191,250) / 225,000.....* 100
= 33,750 / 225,000....* 100
= 0.15 * 100
= 15% decrease <==
For problems like this you can move the y's on the bottem up top by fliping the sign of the exponent (in this case 7 to -7) and MULTIPLYING it with EVERYTHING on top, then because of properties of multplication you can add the exponents to combine them into one term (in this case add 3 and -7 to get -4)

If any of this does not make sense let me know and ill try to clarify better
For this case we must find an expression equivalent to:
By definition of power properties we have to meet:

So, rewriting the expression we have:

Answer:
Option B

(1 + v)(v - 7)
1*(v - 7) + v(v - 7)
1*v - 1*7 + v*v - v*7
v - 7 + v² - 7v
v² - 7v + v - 7
v² - 6v - 7
I hope this helps.