Explain your answer!

40 words

Step-by-step explanation:

120 words/3 minutes is the same as 120 divided by 3

so, you divide 120 by 30 and you get 40 words per minute

Step-by-step explanation:

We are going to make a questioning. Look:

If in 3 minutes she can type 120 word

In    1 min  how many will she type X

We adopt X as a thing witch we don't know. This forms a Rule of three. It happens when we have got 3 values but miss us 1 yet.

Generraly you'll sort the values by type. In this case, I put minutes under minute and words under words.

A Fast way to solve is: multiply where there is not an incognt (1*120) and divide by what left (3)

So:

1*120=120

Divided by 3 (120/3) it's equals 40 words per minute.

Good studies!

-ZehTheJohn

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