21 is the least common denominator of 7 and 3
Answer:
2
Step-by-step explanation:

because 
So,

Which course is this for? I feel like I may need a little more information, but the simplest explanation I can give given the question is:
<em>f(x)</em> is the value of a function <em>f</em> evaluated at the value <em>x</em>. The formal definition of a function is a particular set of rules that associates a particular value with another. For an analogy: you can think of <em>f </em>as a machine that takes in an input, transforms it according to a certain set of rules, and produces an output. <em />In this analogy, <em>x</em> would be the input and <em>f(x)</em> would be the output.
By flipping the fraction of -3/7, you will get the fraction of -7/3 or - 2 1/3.
Therefore, the reciprocal of -3/7 is - 2 1/3.
Hope this helps!