Question 99824
You could with the conversion formula:
1) {{{F = (9/5)C+32}}} or:
2) {{{C = (5/9)(F-32)}}}
Since you want F = C you can substitute in either equation and solve.
1) {{{F = (9/5)F+32}}} Solve for F. Subtract {{{(9/5)F}}} from both sides.
{{{-(4/5)F = 32}}} Now multiply both sides by {{{-(5/4)}}}
{{{F = -40}}}
2) {{{C = (5/9)(C-32)}}} Multiply both sides by 9.
{{{9C = 5(C-32)}}} 
{{{9C = 5C-160}}} Subtract 5C from both sides.
{{{4C = -160}}} Divide both sides by 4.
{{{C = -40}}}
The answer is at -40 degrees the temperature on the Farenheit scale reads the same on the Celsius scale.