Answer: Hi!
To solve this equation, we need to isolate the x. To do this, we will use inverse operations.
The inverse operation for multiplication is division (3 is being multiplied by x,) so we will divide 3 on both sides:
3x/3 = x
21/3 = 7
Our equation now looks like this:
x = 7
You have nothing left to simplify, so you're done!
Hope this helps!