evaluate meantally

3-15+4

-34-6+12

5(-9-4)

5-3(-4)

1/2(-26)

14-21/-7

-5^2

(-5)^2

-8
-28
-65
-13
1
25

To evaluate these expressions mentally, you can follow the order of operations, which is commonly remembered using the acronym PEMDAS (Parentheses, Exponents, Multiplication and Division, Addition and Subtraction).

1. 3 - 15 + 4:
The first step is to perform the subtraction: 3 - 15 = -12.
Then, add the result with 4: -12 + 4 = -8.

2. -34 - 6 + 12:
First, perform the subtraction: -34 - 6 = -40.
Then, add the result with 12: -40 + 12 = -28.

3. 5(-9 - 4):
Start by performing the operation inside the parentheses: -9 - 4 = -13.
Next, multiply the result by 5: 5 * -13 = -65.

4. 5 - 3(-4):
Multiply the number inside the parentheses by the coefficient: 3 * -4 = -12.
Substitute the result back into the expression: 5 - (-12).
To simplify, remember that -(-12) is equivalent to +12.
So, the expression becomes 5 + 12 = 17.

5. 1/2(-26):
Multiply the fraction by the number inside the parentheses: 1/2 * -26 = -13.

6. 14 - 21 / -7:
Perform the division first: 21 / -7 = -3.
Then, subtract the result from 14: 14 - (-3).
Remember that -(-3) is equivalent to +3.
So, the expression becomes 14 + 3 = 17.

7. -5^2:
Start by squaring the number: (-5)^2 = 25.
Since the negative sign is not inside parentheses, it only applies to the number, not the exponent.

8. (-5)^2:
Again, square the number inside parentheses: (-5)^2 = 25.
The parentheses ensure that the negative sign is included in the calculation.

9. -8:
This expression is already in its simplest form, so no further calculations are needed. The answer is -8.

10. -28:
Similarly, this expression is also already simplified to -28.

11. -65:
Again, this expression is already in its simplest form, so no further calculations are required.

12. -13:
This expression is also in its simplest form, so no further calculations are necessary.

13. 1:
Once again, this expression is already in its simplest form.

14. 25:
This expression is also simplified, so no additional calculations are needed.