unexpected EOF while looking for matching `"' - bash simple script

I am learning Raspberry Pi and trying to use code to read my CPU temperature and save it to a file with a bash script. The code is here:

#!/bin/bash
echo ""
cpu=$( $(/opt/vc/bin/vcgencmd measure_temp)"
far=$((cpu/1000))
far2=$((far*9))
far3=$((far2/5))
far4=$((far3+32))
echo "CPU => $((cpu/1000))' C or $((far4))' F"
echo ""
echo "Pi temp $far4 degrees F" > /var/www/html/pitemp.txt

Here is the error:

$ sudo chmod +x checkTemp.sh
$ ./checkTemp.sh

./checkTemp.sh: line 10: unexpected EOF while looking for matching `"'
./checkTemp.sh: line 11: syntax error: unexpected end of file
$ _

Why is it wrong? Here is the instruction I follow.