Evaluating expressions with multiple variable

Rachel is studying the population of a particular bird species in a national park. she observes every 10th bird of that species that she can find in the park. her conclusion is that the birds living in the park who belong to that species generally feed on insects. rachel's sample is . based on the sample she picked, rachel's generalization is

Anumber is equal to twice a smaller number plus 3. the same number is equal to twuce the sum of the smaller number and 1. how many solutions are possible for this situation

Suppose medical records indicate that the length of newborn babies (in inches) is normally distributed with a mean of 20 and a standard deviation of 2.6. find the probability that a given infant is between 14.8 and 25.2 inches long.