Why was it difficult under the articles of confederation to enforce acts of congress

Due to the Articles of Confederation, States could override what Congress had established and create their own laws which caused division between the states and caused many issues on currency and of other sorts of important matters. Thus, enabling no authority of control over the power of the differentiating states.

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