Regarding Question 1, I am not entirely sure whether the following working is consistent with the requirements of the question and/or the current Engineering Studies syllabus, although I thought I'd include it in an attempt to help:
The mass of 50 tonnes is equivalent to 50 000 kg.
This must be converted to a weight force.
The four forces; thrust, weight, lift and drag are then added together using a force polygon.
Because these forces are vectors, they must be drawn tip-to-tail. The figure below shows the forces. The weight force has been drawn first. When all the forces have been drawn, head to tail, the resultant is the vector that is drawn from where you started to where you finished.
The resultant force acting on the aeroplane is 130 kN acting at an angle of 7.5° to the horizontal.
I hope this helps!
