What was a main reason for the crusades? to recapture the holy land from the muslims to gain more trade routes to the east to find an all-water route to the east

The main reason for the crusades, as the people who participated in the crusades named it, was the return of the Holy Land (Israel/Palestine) into the Christian Hands. (recapture the Holy Land from the Muslims). They believed that this was important because it was the land where Jesus lived and people wanted to be able to worship there freely.

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