Quiénes fueron los primeros en utilizar operaciones aritméticas con cierta complejidad?

At noon a tank contained 10cm water. after several hours it contained 7cm of water. what is the percent decrease of water in the tank?

∠1 and ∠2 are vertical angles. ∠2 has a measure of 63°. what is the measure of ∠1 ? enter your answer in the box.

In 3 years, dianna will be 4 times as old as she was 33 years ago. how old is dianna now? translate the phrase "in 3 years" into algebraic terms.