Respuesta :
Step-by-step explanation:
Let the required number be x.
[tex] \therefore \: 3x + 6 = 21 \\ [/tex]
					                   3x+6=21 x would equal 5 because 3 x 5 = 15 and 15 + 6 = 21! answer: 5
					                
					                
					             Step-by-step explanation:
Let the required number be x.
[tex] \therefore \: 3x + 6 = 21 \\ [/tex]