How do i find x and y using what is in the equation

Find the number of positive three-digit even integers whose digits are among 9, 8, 7,5, 3, and 1.

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?

Select the sequences that are geometric.