Please solve this (cpt maths- equations)

Padmavati (Studying) (110 Points)

01 May 2014  

can someone pls. help me with these question.

as far as sum no. 92 is concerned, i substituted x=300, 900 and y=6800, 10400 respectively and got option c as the correct answer. (correct me if the method is wrong)

However, I am unable to solve the next 3 questions.