Aline passes through (2, −1)(2, −1) and (4, 5)(4, 5). which answer is the equation of the line?

5-(1) Y2-Y1 over 4-2 X2-X1.   4 over 2 which simplifies to a positive 2 for Slope.  now you use point slope to find your actual equation 

Y-Y1=M(X-X1)
Y-(-1)=2(X-2)
you will get a positive 1 on the left side of the equation
distribute 2 in with X and -2
you should have Y+1=2X-4
subtract 1 from the left to the right and get
Y=2X-5

that is your equation passing through (2,-1) and (4,5)

X=3 and y=4 is the answer