OK I GOT U so you have multiply the outside with the inside so 2(18k +21)-9 that would be the same thing as 2*18k=36k and 21*2= 42 so that’s 36k + 42 -9 YOU CAN ONLY ADD 42 and -9 because 36k and 42 go together like gummy bears and Mayo… they don’t go together… so only add things that you know how to add because I assume u didn’t already know how to add 36k and 42 because no one came because it’s not possible. Hopefully this helps :)