What is the answer to this and why?

Step-by-step explanation

I get the same answer you do, but I'm not at all certain I'm correct. I would have done it just as you did letting each y value define the new x value and then putting the - on the left in at the very end.

f(1) = 3

f(3) = -1

f(-1) = 7

But there is a minus in front of the left most f. That would make it - 7

sss (side, side, side)

sas (side, angle, side)

asa (angle, side, angle)

aas (angle, angle, side)

hl (hypotenuse, leg)