How do you find the slope of a line from a graph that does not go through the origin?

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?

What does x = in this equation x+3+2x=x+5

What is the range for 31,39,29,34,37,24,36,33,34,28