If you’re asking whether you can get NIT Agartala with 66.9 percentile in JEE Main as an SC candidate, the chances are very low. For NITs including Agartala, SC category candidates typically need a much higher JEE Main percentile and rank to secure a BTech seat through JoSAA counselling, generally a better rank than what a 66.9 percentile would likely give. Actual cutoffs vary by branch and round, and reserved category cutoffs are lower than general, but admission still usually requires a significantly higher percentile/rank.

You can check trends and expected percentiles for NIT admissions here: https://engineering.careers360.com/articles/how-much-percentile-in-jee-main-required-for-nit-btech-admission