Respuesta :

merilynamp
63x+45x   = 108x

You just multiply 3x by 21 and 15 to get 63x and 45x. You then add the like terms to get 108x.
catlover679

3x ( 21 + 15 ) = 108(I know this is not the question but I wanted to solve it.)

Hope it helps! :) :) :)