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 ..
Answer:
19 will be the answer.
Step-by-step explanation:
10+9=19
The first one is -30 seconds
the second one is 20 meters
the third one is 0