How do you know whether to add on both sides or subtract on both sides when solving an equation

Need 50 will mark brainliest answer. find the lengths of all the sides and the measures of the angles.

Solve for x where 0 equation: cot^2x+2cotx+1=0

Currently, the largest cruise ship has a tonnage of 225,282 gross tons (gt). which of the following is a reasonable estimate for the tonnage of this cruise ship? a. 2 × 10^5 gt b. 2 × 10^6 gt c. 2 × 10^-5 gt d. 2 × 10^-6 gt