Here are the most popular articles I’ve written, sorted by category. Full descriptions and a list of all articles are in the articles page. (Contest reflections are located below.)
The VCSMS Program for Inducing Mathematical Excellence aimed to prepare for the qualifying round of the Philippine Mathematical Olympiad. I conducted the program in our school for the years 2016 and 2017. Materials here include lecture notes, past PMO problems sorted by category, and solutions.
A lecture on set theory during PRIME 2017. Image: Marilyn Soriano.
Here are some past problems and answers for recent Philippine contests. Descriptions of the contests and a full list of files are in the contests page.
2018–2019 Season  
Math Wizard  Orals  
Mathira  Orals  
Sipnayan 
Junior High Senior High 

PMO 
Areas writeup Qualifying writeup 

GMATIC  Problems (Joshua Balete) 