Question 1047485
F=(9/5)C+32
F-32=(9/5)C
(5/9)(F-32)=C
When C=F
C=(5/9)(C-32)
but C=(9/9)C
Therefor (9/9)C=(5/9)(C-32)=(5/9)C-(160/9)
moving the (5/9)C over, (4/9)C=-(160/9)
multiply both sides by 9
4C=-160
C=-40
F=C at -40 degrees.