Using the formula C = 5/9(F - 32), what is 77°F in degrees Celsius?

Substitute $F=77$ into the formula: $C=\frac{5}{9}(77-32)=\frac{5}{9}(45)=25$ degrees Celsius, choice G. Do the subtraction in the parentheses first, then multiply by $\frac{5}{9}$. Choice H ($45$) stops after the parentheses and never multiplies by $\frac{5}{9}$. Choice F ($20$) results from using $F-32=36$ instead of $45$. Choice J ($170.6$) is the value of $\frac{9}{5}(77)+32$, which converts in the wrong direction. A temperature of $77^\circ$F is a warm room, so about $25^\circ$C is reasonable.