Blake made an 87 on the first semester of algebra 1. what score must he make on the second semester if he wants to make an average of a 90 for both semesters?

Can someone me with the property questions for 12 13 and 14 plz

Scores on the cognitive scale of the bayley-scales of infant and toddler development range from 1 to 19, with a standard deviation of 3. calculate the margin of error in estimating the true mean cognitive scale score, with 99% confidence, if there are 12 infants and toddlers in a sample.

The difference of three and the reciprocal of a number is equal to the quotient of 20 and the number. find the number.