Acrew will arrive in one week and begin filming a city for a movie. the mayor is desperate to clean the city streets before filming begins. two teams are available, one that requires 200 hours and one that requires "400" hours. if the teams work together, how long will it take to clean all of the streets? is this enough time before the cameras begin rolling?

See below in bold.

Step-by-step explanation:

You work in fractions of the city streets done per hour:

1/200 + 1/400 = 1 /x  where x is the number of hours taken by 2 teams.

Multiply through by the LCM 400x:

2x + x = 400

3x = 400

x =  133.33 hours.

As there are 168 hours in a week they will have enough time.

is this part of a question or something

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