The correct option is B. Distributive property
Given,
On solving the above equation,
multiplying both sides by 3 we, get

now subtracting 21 from both the sides,

dividing both the sides by 2 we get,

Since in the above steps we follow all the giving property except the distributive property.
Hence the correct option is B. Distributive property.
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Answer:
4.39% theoretical probability of this happening
Step-by-step explanation:
For each coin, there are only two possible outcomes. Either it lands on heads, or it lands on tails. The probability of a coin landing on heads is independent of other coins. 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.

In which
is the number of different combinations of x objects from a set of n elements, given by the following formula.

And p is the probability of X happening.
Theoretically, a fair coin
Equally as likely to land on heads or tails, so 
10 coins:
This means that 
What is the theoretical probability of this happening?
This is P(X = 2).


4.39% theoretical probability of this happening