Joe wishes to hang a sign weighing 7.50x10^2 so that cable A, attached to the store, makes a 30.0 degree angle. Cable B is horizontal and attached to an adjoining building. What is the tension of cable B?

Make a sketch first.

The tension in cable A can be resolved into a vertical and a horizontal component.

The vertical component equals the weight of the sign and the horizontal component equals the tension in cable B.

What do you get?