Answer:
[tex]\left|5\right|+\left|-7\right|[/tex]
[tex]rule =a,\:a\ge 0[/tex]
[tex]|5|=5[/tex]
[tex]\mathrm{Apply\:absolute\:rule}:\quad \left|-a\right|=a[/tex]
[tex]\left|-7\right|=7[/tex]
[tex]5+7=[/tex]
[tex]12[/tex]
hope this helps you..
