Write down the equation of the curve
y=f(x−4) The input to f is x−4, not x.
Substitute the x-coordinate of the point
k=f(7−4) The point (7, k) lies on the curve, so put x=7.
Simplify the input
The bracket gives 7−4=3.
Use the given value
This is the fact you are given.
State k
So the point is (7, −2).
Interpret it as a transformation
f(x−4): 4 units RIGHT The curve has been translated 4 units to the right.
Check with the point mapping
(3, −2)→(7, −2) The original curve passes through (3, −2); translating 4 right gives (7, −2).
Note the trap
k=f(11) It is tempting to add 4 to the 7; but the rule replaces x by x−4, so you subtract.
Check the y-coordinate is untouched
no change outside f Nothing is added outside the function, so heights are unchanged.
Final answer
The value of k is −2.