Double the sum of a number and three is the same as the number subtracted by nine

2 (n+3) = n-9

Step-by-step explanation:

2 (n+3) = n-9

Step 1: Multiply (n+3) by two; 2n + 6

Step 2: Subtract n on both sides; n+6 = - 9

Step 3: Subtract 6 on both sides; n = - 9 - 6

Step 4: Add - 9 and - 6; - 15

Solution: n = - 15