math_complementary_equations.sh

#!/bin/bash

print_to_printer=false

while getopts "p" opt; do
  case $opt in
    p)
      print_to_printer=true
      ;;
    \?)
      echo "Invalid option: -$OPTARG" >&2
      ;;
  esac
done

output="\n\n"
output+="Find the complementary equations, and the missing number.\n\n"

num_questions=6

for i in $(seq 1 $num_questions); do
  # Choose a total (target) from 50 to 150
  total=$((50 + RANDOM % 101))
  # Choose one known operand between 10 and (total - 10)
  known=$((10 + RANDOM % (total - 19)))
  
  # Randomly decide the form of equation (1, 2, or 3)
  form=$((1 + RANDOM % 3))

  case $form in
    1)
      # __ + known = total
      output+="$(printf "%1s)  %10s + %2d = %3d" "$i" "____" "$known" "$total")"
      ;;
    2)
      # known + __ = total
      output+="$(printf "%1s) %10d + %2s = %3d" "$i" "$known" "____" "$total")"
      ;;
    3)
      # total - __ = known
      output+="$(printf "%1s) %10d - %2s = %3d" "$i" "$total" "____" "$known")"
      ;;
  esac
  
  output+="\n\n\n\n\n"
done

# Output or print
if $print_to_printer ; then
  (figlet "Complement Equations"; echo -e "$output") | paps | lpr
else
  figlet "Complement Equations"
  echo -e "$output"
fi