can someone help with these 3 questions, they are in the pictures!

Question One
y = v - 1/2 g t^2   Subtract v from both sides.
y - v = - 1/2 gt^2  Multiply both sides by - 1
-(y - v) =  1/2gt^2 Remove the brackets.
v - y = 1/2 gt^2 Divide by g
(v - y)/g = 1/2 t^2 Multiply by 2 on both sides
2(v - y)/g = t^2 Move the 2 to the denominator on the left.
(v - y) / 0.5g = t^2 Take the square root of both sides.
sqrt [ (v - y) / 0.5g ] = t 

Answer: B or second one down <<<<<<<

Question Two  
There are no minuses in the answer. That eliminates 2 and 3
km^2 - c = n   Add c to both sides.
km^2 = c + n  divide both sides by k
m^2 = [c + n]/k  Take the square root of m^2
m = sqrt [(c + n)/k]

Answer A or the first one.

Problem 3
This is an estimation question. One value of x is <0 the other > 0
The two graphs cross when x = a bit over 2 and x < about - 5
The answer is C 2.1 and - 5.1 about.

Answer: 2.1 and -5.1 
Answer: C <<<<<<<<<