What is the (slope) rate of change and the equation?

Simplify a7/a4 a) 1/a3 b)-a/a2 c)a4/a3 d)a3

What is the value of x? enter your answer in the box. photo attached.

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?