1. Solve for x or y.

(a)

<-------4m--------><--------4m-------><-------------- xm ------------>
______________________________________________________________________ 		
^                  ^                 ^                               ^
25N               5N                 ^                              15N

(b)

<-----5 -----><---3---><---2---><----3----><---------- x ---------->
____________________________________________________________________
^            ^        ^         ^          ^                       ^
10N         10N      15N        ^         8N                      9N

(a) The graphics didn't come through very well but I assume that you have a beam with a 15 N force at the end, a 25 N force 4 m away from it, a fulcrum another 4 m from the 25-N force and a 5 N force that is x m on the other side of the fulcrum. If this is the case then you know that the system is balanced and so the sum of the moments (rotational effect) of  the 2 forces on the the one side are balanced by the moment of the force on the  other side. Remember that the moment is calculated by multiplying the size of the force by the distance of the force from the fulcrum. On the one side the sum of the moments is: 25*8  +  5*4  =  220. On the other side the moment is  15*x. So  15x  =  220  etc.

(b) Use the same reasoning for this one.