Answer: Please see attached images 
(2nd image is the answer, 1st image is it worked out)
Explanation:
You are given "Use synthetic division to divide 
 by 
"
1) You first take the coefficients from the expression, 
, and place them in a row.
 
 | 1 6 15 24 
 |__________________
2) Next you take the expression, x + 3, and take the last coefficient and put it to the left.
3 | 1 6 15 24 
 |__________________
3) Next you drop the 1 (this is the case for the first number of any synthetic division problem)
3 | 1 6 15 24 
 |__ ↓_______________
 1
4) Now you multiply 3 and 1, then place that product under 6.
3 | 1 6 15 24 
 |__ ↓__ 3___________
 1
5) Then you subtract the column: 6 - 3, and put the answer below
3 | 1  6 15 24 
 |__ ↓__ 3___________
 1 3
6) Now you repeat this process (steps 4-5) but with the following numbers. So repeating step 4, You multiply 3 and 3, and put that product under 15.
3 | 1  6 15 24 
 |__ ↓__ 3__ 9________
 1 3
7) Repeating step 5, you subtract the column: 15 - 9, and put the answer below.
3 | 1  6 15 24 
 |__ ↓__ 3__ 9________
 1 3 6
8) Once again, you repeat steps 4-5. So repeating step 4, you multiply, 3 and 6, and you place the product under 24.
3 | 1  6 15 24 
 |__ ↓__ 3__ 9___18____
 1 3 6
9) Repeat step 5, you subtract the column: 24 - 18, and put the answer below.
3 | 1  6 15 24 
 |__ ↓__ 3__ 9___18____
 1 3 6 | 6 
To find the quotient, that is result of the synthetic division but with its variables, and not including the remainder.
 Quotient: 

The remainder is the remaining number that is at the bottom of the last column.
Remainder: 6