Blackboard with a sum of a question mark and a light bulb

Related tags:

• blackboard
• fail
• chalkboard
• mistake
• chalk
• 3
• education
• study
• board
• wrong
• education symbol
• plus sign
• school
• plus
• bussines
• sign
• question
• business man
• light sign
• bulb
• bulb light
• holding
• symbol
• number
• error
• signboard
• equality
• 21+