Question

Find the missing number(?) so that the equation has no solutions. ?x+3=3(-x+7)

Answer 1

I think the answer is -3

Answer 2

?x+3=3(-x+7)

?x+3=-3x-21

?x = -3x-21-3

?x +3x = -24

(?+3) x = -24

the equation has no solutions if  (?+3)=0
?+3=0
? = -3