Jewish christians who taught legalism in the churches were called:

Legalism (or nomism), in Christian theology, is the act of putting law[clarification needed] above gospel by establishing requirements for salvation beyond repentance and faith in Jesus Christ and reducing the broad, inclusive, and general precepts of the Bible to narrow and rigid moral codes.[1] It is an over-emphasis of discipline of conduct, or legal ideas, usually implying an allegation of misguided rigour, pride, superficiality, the neglect of mercy, and ignorance of the grace of God or emphasizing the letter of law at the expense of the spirit. Legalism is alleged against any view that obedience to law, not faith in God's grace, is the pre-eminent principle of redemption. On the Biblical viewpoint that redemption is not earned by works, but that obedient faith is required to enter and remain in the redeemed state.

Use the formula: (n-2)×180, where n is the number of sides(18-2)×180= 28800, now this is the full exterior angle of 18-gon so you divide it by 18.28800÷18=160