The cost of gasoline tripled in the past 12 years. If gasoline cost n dollars and r cents per gallon 12 years ago, how much does it cost now?

Step-by-step explanation:

step one:

In this problem, we are told that the price of gasoline has tripled in the past twelve years.

step two:

Given that the price 12 years ago was $n and r cent

to get the current price we need to multiply the price twelve years ago by 3

hence n*3 and r*3

this means that the current price is

3n dollar and 3r cent

The price now is 3n dollar and 3r cent

32/80  

91/140

the last one 54 doesn't go into 45. 54/100 ?

step-by-step explanation:

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