Final answer:
To simplify the given expression, calculate the sum inside the first set of parentheses, change the signs and calculate the sum inside the second set, and finally subtract 12 from the combined result. The simplified expression is 17.
Step-by-step explanation:
To simplify the expression (8 + 3 + 7) - (3 - 7 - 7) - 12, let's perform the operations inside the parentheses first. For the first set of parentheses: 8 + 3 + 7 = 18. For the second set of parentheses, we need to change the sign of the numbers being subtracted: 3 - 7 - 7 becomes 3 + (-7) + (-7), which is -11. Now, let's put the simplified terms from the parentheses back into the expression, along with the -12 at the end: 18 - (-11) - 12 = 18 + 11 - 12 (since subtracting a negative is the same as adding a positive). Add the numbers: 29 - 12 = 17. So, the simplified expression is 17.