Answer:
The value of given expression is 0, where m=21 and n=12.
Step-by-step explanation:
The given expression is
[tex]\dfrac13m-1-\dfrac12n[/tex]
substitute m=21 and n=12 in the above expression.
[tex]\dfrac13m-1-\dfrac12n=\dfrac13(21)-1-\dfrac12(12)[/tex]
[tex]\dfrac13m-1-\dfrac12n=7-1-6[/tex]
[tex]\dfrac13m-1-\dfrac12n=7-7[/tex]
[tex]\dfrac13m-1-\dfrac12n=0[/tex]
Therefore the value of given expression is 0, where m=21 and n=12.