How to tell if a triangle is obtuse or acute

If 10 men take 18 days to mow 60 acres of grass, how long will 15 men take to mow 80 acres?

What is the factored form of the following expressions? d^2 – 13d + 36

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.