It is confusing to memorize formulas. To start with, just remember the standard values; freezing and boiling points of water expressed in C and F. Knowing these data provide the important conversion formula that can be derived from it.
"Freezing Point of water in " C and F=0^o and 32^o
"Boiling Point of water in " C and F=100^o and 212^o
Now, formulate the ratios that relate the two temperature scales where the temperature units and zero points are different; hence,
(C-0)/(100-0)=(F-32)/(212-32), simplify
C/100=(F-32)/180, cross multiply
100(F-32)=180(C), divide both sides by 100 and simplify
(cancel(100)(F-32))/cancel(100)=(cancel(180)9(C))/(cancel(100)5, simplify
F-32=9/5(C), add 32 both sides of the equation
Fcancel(-32+32)=9/5(C)+32, simplify
color(red)(F=9/5color(blue)((C))+32-> "the derived formula"
Then, given the value color(blue)(C=260^o), plug in the value to the formula to convert C to F; hence
F=9/5(C)+32
F=9/5(260)+32
F=468+32
F=500^o
