You will see these right triangle triples on your End Of Course Test, your PSAT, and your SAT. It's worth knowing them by heart because it will save you time and build your confidence. There are many sets of triples that work for right triangles but here are the ones you need to know.
( 3, 4, 5) ( 5, 12, 13) ( 7, 24, 25) ( 8, 15, 17) ( 9, 40, 41)
You and a friend work on these together until you both know them by heart.