Please solve question no 36.....

Dear student,
The question asked by you has been tagged with the inappropriate grade and hence we will not be able to provide you with the required academic assistance in this thread. This is the question of linear equation in three variables which is not in 7th standard. 
We request you to please ask question with the correct grade subject tagging, this will help us in connecting you with the suitable expert.
Keep posting!
Regards