Please explain and need help as soon as possible

Write the rational number in lowest terms 99/-15

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?

Which of the following pair(s) of circles have las a common external tangent? select all that apply. a and b a and c b and c