Q1
40+45+45+50+50+60+70+75+95+100=630

Mean=630/10=63
Median=(50+60)/2=55

Scores greater than the median are:60, 70, 75, 95, 100

Scores less than the mean: 60, 50, 50, 45, 45, 40

Only number in both sets is 60

So answer is 1

Q2

y=(x+a)(x+b)
y=x^2 + ax + bx + ab

(1):a+b=-1

y=x^2 + x(a+b) + ab
y= x^2 +1x + ab

Insuff

(2): Intersects y-axis at (0,-6)

-6=0 + 0 + ab
-6=ab

Insuff

Combined:

y=x^2 + x -6


y has to be 0 for it to intersect the x-axis

0=(x-3)(x+2)
x=-2 | x=3

crosses at the axis at (-2,0) and (3, 0)

so C is the answer

Q3:

Refer to this post:

https://www.beatthegmat.com/functions-t21540.html