x/8+x/12+x/2+28=x ?

how to solve this equation?
do I have to fine same common denominator?

Yes. Find a common denominator (24 in this case), combine the x terms, and solve

(3x + 2x + 12x -24x)/24 = -28
-7x/24 = -28
x = (28*24/7) = 96