Answer
$y=60t+550$
Work Step by Step
Let y represent the imports of mercury (in millions of kg)
as a linear function of t, the number of years after 2210.
The model: $y=mt+b$.
The unit of slope is: (units of y) per (unit of t),
that is "million kg per year".
The problem text gives us "$60$ million kg per year",
that is, $m=60$
So far, $\quad y=550t+b$
The intercept, b, is the value of y when t=0.
The text gives us $b=550.$
Thus,
$y=60t+550$ (million kg of mercury)
