M for which -x² + 8 + m = 0 will have positive roots​

Cassie is traveling 675 miles today to visit her brother and his family. so far, she has stopped for gas three times. at the first stop, she put in 7.1 gallons of gas and paid $23.79. at her second stop, she put in 5.8 gallons of gas and paid $19.08. and, at the third stop, 6.6 gallons and paid $20.39. at which stop did casey pay the most for gas?

Sum of the interior angles of a pentagon

The volume of a box varies directly with its length if a box in the group has a length of 30inches and k=24 what is its volume