Answer:
x=10
Step-by-step 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.
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
