And what you should do next, is we have these

three forces as vectors, these three unknown forces as vectors.

We have this known reaction force, and so we

are going to have to apply the an equation of equilibrium.

In this case, this is a concurrent force distance, so

a moment equation is not going to do us any good.

So let's go ahead and sum forces vectorially

at point B to come up with our equation of equilibrium.

And so in this case I've got minus

75 in the i direction for that force

plus each of three forces. So plus FBD i,

plus 3 5ths FBA i, minus 4

5ths FBA j. Minus 4 over the square root

of 160 FBC j, plus 12

over the square root of 160 FBC k.

And all that has to equal 0. And what next?