[root@local]  num_a=10
[root@local]  num_b=3

方式一：
[root@local]  echo  $((${num_a}+${num_b}))
[root@local]  echo  $((${num_a}-${num_b}))
[root@local]  echo  $((${num_a}*${num_b}))
[root@local]  echo  $((${num_a}/${num_b}))
[root@local]  echo  $((${num_a}%${num_b}))
[root@local]  echo  $((${num_a}**${num_b}))

方式二：
[root@local]  echo | awk "{print ${num_a}+${num_b}}"
[root@local]  echo | awk "{print ${num_a}-${num_b}}"
[root@local]  echo | awk "{print ${num_a}*${num_b}}"
[root@local]  echo | awk "{print ${num_a}/${num_b}}"
[root@local]  echo | awk "{print ${num_a}%${num_b}}"
[root@local]  echo | awk "{print ${num_a}^${num_b}}"