Temperature on two 7-segments displays
The show() function already has support for specifying the first pin of the display. So if the second digit is starting at pin 8 and connected in the same order then it should be as simple as:

// Output a 2 digit decimal value.
void show_2digit_decimal(int num) {
  // force value to displayable range because show() doesn't do any sanity checks
  if (num &lt; 0)
    num = 0;
  if (num &gt; 99)
    num = 99;
  // display it.
  show(0, num%10);
  show(8, num/10); // int/int always rounds down to the nearest int
}


You will also have to add the appropriate pinMode(&lt;pin&gt;, OUTPUT); commands to the setup() function to make the pins outputs.

----- update

To get the temperature to display first get rid of these lines, they aren't doing anything useful

static int temp = DHT11.fahrenheit();
static int digit_0 = temp % 10;
static int digit_1 = temp - digit_0;
static int digit_2 = digit_1 / 10;


And then change the loop function to being

void loop() { 
  show_2digit_decimal(DHT11.fahrenheit());
  delay(500);
}


Although unless the teacher is completely incompetent you should have been able to work that out yourself, it's not exactly rocket science. If unsure take a guess and try it first before asking. The logic is simple enough that you should be able to work it out. For syntax errors the compiler error messages will normally tell you exactly what's wrong.