The formula for a sequence or series used to find any term in that sequence or series

Which term best describes the association between variables a and b

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?

Complete the solution of the equation. find the value of y when x equals to 6 4x+y=20