If y is proportional to x and y = -15 when x = -20, what is the value of x when y = 12?

According to modern science, earth is about 4.5 billion years old and written human history extends back about 10,000 years. suppose the entire history of earth is represented with a 10-meter-long timeline, with the birth of earth on one end and today at the other end.

Given the equation f(x)=a(b)x where the initial value is 40 and the growth rate is 20% what is f(4)

Evaluate cos2θ for cosθ = square root of 3/2