im confused on this one someone plz help me

Question

3x - 3 = 15
a. 4
b. 5
c. 6
d.7

Answer 1

i think its b but im not sure check this 4 me

Answer 2

If you "think" it is b) then why did you not try that choice?
if x=5, then
left side = 3(5)-3 = 15-3 = 12
right side = 15

nope, it's not b)

Answer 3

add 3 to both sides and you get
3x = 18
...

Answer 4

or, since you appear to have guessed 5 because 15/3 = 5,
just be sure to divide everything by 3, giving you
x-1 = 5
...