Answer
The median income of a 50 years old U.S. resident is higher than a 40 years old U.S. resident.
Work Step by Step
$x=40$:
$ŷ=-55961.675+4314.374\times40-45.66\times40^2=43557.285$
$x=50$:
$ŷ=-55961.675+4314.374\times50-45.66\times50^2=45607.025$
$45607.025\gt43557.285$
