Test

count=10
right=0
while test $count -ne 1
do
  ((a=$RANDOM%30))
  ((b=$RANDOM%30))
  ((c=a+b))
  read -p "$a+$b=" r
  test $c -eq $r && echo "Right";((right=right+1)) || echo "Wrong"
  ((count=count-1))
done
echo "Right: $right"