we know that
If two numbers have a sum of zero, then we say they are additive inverses
Let
x--------> the additive inverse of the increased of temperature
y--------> the increased of temperature
we know that
[tex]x+y=0[/tex] ---------> equation
in this problem we have
[tex]y=20\° F[/tex]
substitute the value of y in the equation
[tex]x+20\° F=0[/tex]
Solve for x
[tex]x=-20\° F[/tex]
therefore
the answer is
the additive inverse of the temperature increase is [tex]-20\° F[/tex]
