4x2 divided by 3 please help thanks you

What number should be added to both sides of the equation to complete this square? x^2-10x=7

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?

The cost of using a service is $0.25 per min. what equation correctly represents the total cost c, in dollars, for d days of use?