Hello Ronak,
For Economics hons, in 10+2 math is compulsory.
You should have maths as a subject in class 11th & 12th . It is compulsory.
The basic eligibility criterion for pursuing B.A. (Hons.) (Economics) degree is qualifying 10+2 or equivalent examination in any stream from a recognized board of the country. Some universities and colleges give preference to students who have studied Economics as a subject at 10+2 level.
Thank you.

Hello
To take eco honours as a course for your undergraduate you need to have a higher secondary certificate qualification from a recognised board with a minimum aggregate of 45%.
Bachelor of arts (B.A) honours in economics is a 3 year full time graduation course. The entire course of 3 year duration is covered in 6 semesters of 6 months each. Some Universities follow yearly program as well. The cut off differs from each University. Some Universities take entrance exams for admission like

1- Christ University, Bangalore
2- st.mira's college for girls,Pune

Top institutes offering B.A in economics are-

Lady shri ram College for women, New Delhi
Loyola College,Chennai
Christ University,banglore
Miranda house college, Chennai
Hindu College, New Delhi
Hansraj College,New Delhi etc
Fees for government colleges is nominal ranging from 1400 to 10,000 RS annually

This course offers students to seek a career in trade and commerce and banking sector of economy as it offers them a highly detailed and comprehensive study of basics of economics.
Such graduates may be hired as sales Analyst, economic research, customer profit analyst, investor administrator etc in areas such as analysis/forecasting firms, stock exchange, manufacturing firms etc.
I hope this helped.
Feel free to ask any other query.