No, they forgot to switch variable labels after solving for the independent variable...
y=-8x+4
y-4=-8x
(y-4)/-8=x
Now that you have solved for the independent variable x, you switch the variable labels...
y=(x-4)/-8
f^-1(x)=(x-4)/-8 which should really be rewritten as:
f^-1(x)=(4-x)/8 :P
It would be 1,800 because when you round 34 it becomes 30 and when you round 57 becomes 60 and 30 x 60 = 1,800. This helps me round remember "4 or less let it rest, 5 or more raise the score" hope that makes rounding easier!!
Do you have an image attached so I can help you?
