Explanation:
Substitute 86 ⁰F into the given equation:

Subtract 32 from both sides:

Divide each side by 1.8:

If the temperature is 86 ⁰F, that is equivalent to 30 ⁰C.
Substitute 40 ⁰C into the equation:

Multiply:

Add:

If the temperature is 40 ⁰C, that is equivalent to 104 ⁰F.