□+○+△=40 □+○+△+△=50 □+○+○+△=60 问□等于多少 △等于多少 ○等于多少

□+○+△=40 ①
□+○+△+△=50 ②
□+○+○+△=60 ③
②-①,得
△=50-40=10
□+○=40-10=30 ④
□+○+○=60-10=50 ⑤
⑤-④,得
○=50-30=20
□=30-20=10
综上所述□=10,○=20,△=10