31.+ addition
32. - subtraction
Answer:
D
Step-by-step explanation:
Divide 12 by all of the ingredients then multiply them by 18
The interval

corresponds to the part of the distribution lying within 2 standard deviations of the mean (since 500-2*100=300 and 500+2*100=700). The empirical rule states that approximately 95% of the distribution is expected to fall in this range.