[16] f(-3) = -5
#17 is asking us to find what the function equals when x is equal to -3. We will find x = -3 on the graph, then find what y equals.
[17] f(4) = 0
#17 is quite similar, it is asking us to find what the function equals when x is equal to 4. We will find x = 4 on the graph, then find what y equals.
You asked in the comments for #16 and #17, I hope this helps.
