and thus is one of the previous two types of problem
Source: Solving Mathematical Problems (2nd ed., 2006), Ch. 1 : Strategies in problem solving
Terence Tao: 1 quote0 likes
Terence Chi-Shen Tao is an Australian-American mathematician who has worked in various areas of mathematics. He currently focuses on harmonic analysis, partial differential equations, algebraic combinatorics, arithmetic combinatorics, geometric combinatorics, compressed sensing and analytic number theory. As of 2015, he holds the James and Carol Collins chair in mathematics at the University of California, Los Angeles. Tao was a co-recipient of the 2006 Fields Medal and the 2014 Breakthrough Prize in Mathematics.

and thus is one of the previous two types of problem
Source: Solving Mathematical Problems (2nd ed., 2006), Ch. 1 : Strategies in problem solving