What is - 3 (m+6) - (11+9m)

First use the distributive property to multiply the first set of parentheses with the - 3 and the second parentheses flip the signs because its negative

(-3m-18) + (-11-9m)

Then remove parentheses because it is addition and combine like terms

-12m - 29

-3 (m+6) - (11+9m)

distribute

-3m - 3*6 - 11-9m

-3m - 18 - 11-9m

-12m - 29