Respuesta :
Answer:
3 is the missing answer.
Step-by-step explanation:
7 * 3 = ( _ * 3) + ( 4 * 3)
21 = ( _ * 3) + 12 -Multiply 4 * 3 and 7 * 3
9 = _ * 3 -Divide both sides by 3
3 = missing number
7x3=21 4x3=12 21-12=9 9/3 is 3 so the missing number is 3