can someone explain on how justification is done in constructions, i just dont seem to understand this concept, my pre boards are on monday so please reply soon.

And also how should aim to solve sums in areas of parallelograms and triangles, any clues or hints?

Dear Student!

Justification is done in order to check whether the figure which we have construct is correct as per the conditions given in the question. It is done by comparing the given measurements and measurements obtained after construction of a figure or by verifying any property like congruency, similarity, pythagoras theorem etc. which ever is suitable for the given figures like circles, triangles etc.

In order to solve the sums related to area of parallelograms and triangles, you need to remember various theorems and properties related to these two figures and also their use at the correct place. 

All the best for your exam!!!