Can you please check my work? You have helped other students I know. Thank you:)

Question

Multiply
-7(2a2 -4) = -14a2 + 28

Multiply
0.5(a + b -5) = 0.5a + 0.5b - 2.5

Factor
bx - by + bz = b(x - y + z)

Combine like terms (simplify)
12x + 4 - 11y - 6x - 9 - y = 6x - 12y - 5

Evaluate the expression
3x2y when x = 3 and y = 5
Answer: 135

Write as a fraction and simplify
Z-4
Answer: 1/z-4

Write using negative exponents
1/64
Answer: -6-4

Multiply and simplify
3-small2 • 3small6 = 81

Divide and simplify
4-small2/4small4 = 16

Divide and simplify
Y/y-5 = 1

Simplify
(2small3) -small2 =32

Simplify
(x-small1 ysmall1) small5 = ysmall5/xsmall5

Write in scientific notation
0.000005 = 5x10 -small6

Write in standard notation
31 x 10small7 =310,000,000

Perform the indicated operations (give your answer in scientific notation)
(5x10small2) x (5.6x10small4) = 2.8x10small6

Solve
X - 2.1 = -7.5
Answer: x = -5.4

Solve
2.3 = -y/2
Answer: y = -4.6

Solve
2 - x = 11 (x - 1)
Answer: x = 13/12

Please check my answers.

Answer 1

Did you see lidia's response?

http://www.jiskha.com/display.cgi?id=1320785885

Answer 2

Yes! Great! I wasn't sure if she was a tutor or not thank you.

Answer 3

Many of our questions are answered very well by other students.

I'm not really a math teacher, so I defer to answers that appear to be reasonable.

Answer 4

Evaluate the expression 3x2y when x = 3 and y = 5.