We must subtract 12u + 7v from 20u + 13v.
1) Applying the associative property of the sum, we have:
[tex](20u+13v)-(12u+7v)=(20u-12u)+(13v-7v)\text{.}[/tex]2) Computing the difference of each parenthesis, we get:
[tex]8u+6v\text{.}[/tex]Answer
[tex]8u+6v[/tex]