First, fill in the variable that you know (F) with 158. Now you have the equation C= 5/9 × (158 - 32). According to PEMDAS, you solve parentheses first, so you get C= 5/9 × (126). Next, you do multiplication, which is 5/9 × 126. To make it simpler, you can do 5/9 × 126/1, then you can simplify it further to 5/1 × 14/1 to get 70/1 or 70.