after +2 diploma aur B.Tech

Didn't perform very well in +2 even i have to give supply in math. i want to take add on lpu but want 60%. but i dont score to much marks to reach 60%. They are telling that if i passed in +2 then they will give me add in diploma 2nd year after b.tech 3rd year should i go aur repeat+2 help me plzz