Statics questions to make it correct, do we only need to remove x4

hello,

For the first picture

1-to make it correct, do we only need to remove x4 ? If yes, why shouldn’t we use it?

2- why did we use sin not ( cos ) ?

For the second picture

I think the correct answer is inside the square, if it is not correct please correct it.

Questions:

1- why we didn’t use minus ( – ) like the first picture

2- why did we used ( cos ) for Fx, and we used ( sin ) for Fy ?

3- why did we used 5m with Dx and Dy, and why the first time with ( cos ) and the second time with ( sin ) ?