三个 (sān gè) combines the number three (三) with the general measure word 个. It is one of the most common number-measure combinations in Mandarin, used before general nouns for people and objects. 三个人 (three people), 三个问题 (three questions), 三个月 - wait, months use 个 too (三个月, three months). Learning number + measure word combinations is fundamental to Mandarin numerals; 个 is the default when no specific measure word applies.