HELP (explanation needed too)

25,000,000

20,000,000 + 5,000,000

A) 4 x 10^5

400,000

A is not the answer.

B) 9 x 10^4

90,000

B is not the answer.

C) 4 x 10^3

4,000

C is the answer.

D) 9 x 10^3

9,000

D is not the answer.

answer: what are the following choices

the solution of the equation is 2.23 ⇒ answer b

step-by-step explanation:

* lets revise the meaning of exponential function

- the form of the exponential function is y = ab^x, where a ≠ 0, b > 0 ,  

  b ≠ 1, and x is any real number

- it has a constant base b

- it has a variable exponent x

- to solve an exponential equation, take the log or ln of both sides,  

  and solve for the variable

* lets solve the problem

∵

- the base is 7 and the exponent is x

- insert ㏑ in both sides

∴

- use the rule

∴ x ㏑(7) = ㏑(77)

- to find x divide both sides by ㏑(7)

∴

* the solution of the equation is 2.23 to the nearest 2 decimal places