Answer:
C. 3
Step-by-step explanation:
Given expression is:

We know that the rules of exponents are used to solve these kind of questions.
When there is exponent on exponent like in this question 1/7 has an exponent of 7 , the exponents are multiplied.
So,

The 7's will be cancelled out and remaining power will be 1

Hence, option C is correct ..
We know that 3/10*20=6 students are eating salads.
We also know that 3/5*20=12 students are eating sandwiches.
Assuming each person only eats one thing, there are 20-12-6=2 students eating lunches other than salads or sandwiches.
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