Question

What is the answer to 3x-9=21

Answer 1

3x-9=21

Move -9 to the other side. Sign changes from -9 to +9

3x-9+9=21+9

3x=30

divide by 3 for both sides

3x/3=30/3

Cross out 3 and 3, divide by 3 and then becomes 1*1*x=x

x=10

Answer: x=10

Answer 2

x=10

Explanation:

Any number next to x like 3x you multiply so you take numbers 1-9 and put it as X and work through every number and see which number makes the equation true.