remember you can do anthing to an equaiton as long as you do it to both sides
I think you are missing a relation symbol at the end
it could be an equals though (just my guess)
For which value or values are the expressions 15k+9 and 3(2k+3)+9k equal
15k+9=3(2k+3)+9k
use distributive prpoerty which says
a(b+c)=ab+ac so
3(2k+3)=6k+9
now we have
15k+9=6k+9+9k
add like terms
15k+9=15k+9
subtract 9
15k=15k
divide 15
k=k
since this is a true statement, any number will work for k
k=all real numbers