work done by force

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Use trig to resolve F2 into orthogonal components: one acting in the same direction as F1 and the other component acting in the same direction as F3.

but I don't need to resolve the vector 

Yes you do!  The work done by F₂ is the component parallel to the incline's surface (F₂cos(30°)) multiplied by the distance moved.

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yes that's right Now I get it  

can you also help me here 

Thank you Alan now its very clear