Answer:
5
Step-by-step explanation:
3(3x+7) = 3x+51
9x + 21 =3x+51 ; cuz 3 times 3 is 9 and 3 times 7 is 21
subtract 21 so 21 - 21 = 0 and 51 - 21 = 30 so
9x= 3x+30
Then subtract 3! 9-3x and 30 - 3x
You will get 6x = 30
Next you will divide by 6x
Lastly you will get 5! So your answer is 5, sorry it's a little messy but I hope this helps!