D = 1/2 a t^2 is given. And it wants you to find t in terms if a and d. Which means, you need to arrange the equation and let t be alone.
If you let t^2 alone ;
2d/a = t^2
And square root t^2 will give you t ;
SquareRoot(2d/a) = t
The answer is (2)
Try multiplying the original price by the decimal so for example 22.50x0.18
Answer:

so B is the answer 
Step-by-step explanation:

4^7=16,384 i used a calulator
Your answer would be -1/6