A pencil cost #(x-5)and an exercise book cost #(2x+10.if the sum of the cost of the two items is divided by 7,the result is #5.00.calculate the cost of an exercise book.

Need this asap if anyone can i would be very grateful. if you could show workings that would really

Sanya noticed that the temperature was falling at a steady rate of 1.4 degrees every hour from the time that she first checked her outdoor thermometer. by 6 a.m., the temperature had fallen 21 degrees. which expression can you use to find how many hours earlier she had first checked the thermometer?

How can constraints be used to model a real-world situation?