Question 211881
Lets break this into pieces.  "If three is added to a number..."  Let the number be x and add three.  x+3

"...the sum is tripled..." The x+3 should be added together before the multiplication is done so we need to use parenthesis to change the order of operations.  3*(x+3)

"...the result..." means we are finished with the left side of the equation and need to enter an =.  So the equation starts out 3(x+3)=

"...is 27 more than the number."  27+x

Now we know what each side of the equation is so put it together and get:
3(x+3)=27+x

Next, solve for x. 
Step 1. distribute 
3x+9=27+x

Step 2. subtract x from both sides of the equation.
3x+9-x=27+x-x

Step 3. combine like terms.
2x+9=27

Step 4. subtract 9 from both sides of the equation.
2x+9-9=27-9

Step 5. combine like terms.
2x=18

Step 6. divide both sides by 2
2x/2=18/2 

x=9

Or for a slightly different explaination:
*[invoke explain_simplification "3(x+3)=27+x" ]