out of 80 student ss3 if each student offer at least one of chemistry and physics if 50 student offer chemistry and 42 offer physics.How many student offer chemistry only

1 answer

no idea what the "ss3" means.
if all take something, then if x take both,
50+42-x = 80
find x, and then 50-x do chemistry only

review Venn diagrams and inclusion-exclusion