Step-by-step explanation:

Division of a fraction is the equivalent of multiplying by its reciprocal
ex.

i suggest you try to remember this concept
in terms of your question
from this point, just multiple the numerators together and denominators together, then simplify if necessary
fyi- difference of squares

relating that to

also a side note, you might want to factor out the 4 first in the top fraction
The answer is x = 15
The equation would be x + 2 = 17
Answer:
We should expect 25 generated digits in order to get a fifth "4"
Step-by-step explanation:
For each generated digit, there are only two possible outcomes. Either it is a four, or it is not. The probability of a digit being a 4 is independent of other digits. So we use the binomial probability distribution to solve this question.
Binomial probability distribution
The binomial probability is the probability of exactly x successes on n repeated trials, and X can only have two outcomes.
The expetcted number of trials to get r sucesses, with p probability, is given by:

Assume that the calculator will generate a "4" on any given attempt with probability 0.20.
This means that 
How many total generated digits should we expect in order to get a fifth "4"
This is E when r = 5. So

We should expect 25 generated digits in order to get a fifth "4"
Third piece = 6 feet />l=large
(3l+3) +(1/3l)+2 +l =15
multiply everything by 3
3l-3 +l+6+3l = 45
7l = 42
l = 6 (3rd piece) All pieces =6 + 5 +4 = 15