To find the probability that a randomly selected student is in 9th grade and chose pizza, you will use the following formula for probability:
\[ P(A) = \frac{\text{Number of favorable outcomes}}{\text{Total outcomes}} \]
In this case, the number of favorable outcomes is the number of 9th graders who chose pizza, which is given as 30. The total number of students surveyed is given as 126.
Now, calculate the probability:
\[ P(\text{9th grade and pizza}) = \frac{30}{126} \]
To simplify this fraction, you can divide both the numerator and the denominator by their greatest common divisor (GCD). The GCD of 30 and 126 is 6.
\[ P(\text{9th grade and pizza}) = \frac{30 \div 6}{126 \div 6} = \frac{5}{21} \]
Therefore, the probability that a randomly selected student is in 9th grade and chose pizza is:
\[ \frac{5}{21} \]