Hopefully I’m not too late, but here’s how I solved it. Basically, replace F with 68. Subtract 32 from both sides so your equation becomes 9/5C=36. Divide both sides by 9/5 so C is left but itself (C=36/1.8). The answer should come out to 20. If you want to check my answer, plug 20 into the equation. Multiply 20x9/5 which equals 36. Add 36 and 32 together to get 68. Hope this helps