I've done the work for Algebra1 can someone check it?

Question

1)Write 6.92x10^-5 in standard form
.0000692

2)Write3,400 in scientific notation.
3.4x10^3

3)12+4x10
52

4)(-1)^2x4
4

5)(3^2)(-4^2)
144

6)(4x^3y^4)(3x^2y)
12x^5y^5

7)(s^3t)^2
s^6t^2

8)54m^3/9m^4
6/m

9)(-5xy+2xyz)+(xy-3xyz)
4xy-xy^2

10)(4a-3b)-(a-5b)
3a+2b

11)Reduce to lowest terms:
-3c^3d/-9c^2d^3
(1/3)(c/d)

Solve:
12)13x+21=60
x=3

13)7/y=5/8
y=11.2

14)Find the common monomial factor. Divide to find another factor. Then write the polynomial as the product of the monomial and a polynomial.
15m^2n^3+3mn^2+6n
i got help on this one and got 3n(5m^2n^2+mn+6)

15)Multiply(m-4n)(m-4n)
m^2-8mn+16n^2

16)5x^4-2x^2-(-x^4-x^2)
6x^4-x^2

17)-20b^2/3a x 15a^3/5b
-20a^2b

18)-10+(-30)
-40

19)(-1)^5
-1

20)m(9m^4)
9m^5

21)5y+y+2y
8y

22)(2c-3d)-(-7-2d)
9c-d

23)Joe has $21 more than Fred. Together, they have $177. How much does each have?
J=99
F=78

24)5s+3t=19
5s-3t+1
2,3

25)x-y=3
x+y=-1
2,1

Their all practice problems from my book. Working with numbers Algebra1.

Answer 1

Is this an exam or quiz? I really don't want to let you know which are correct or not if it is a test of some kind. I will tell you this though. Some of the answers are incorrect. I found at least 4, but I did not check every problem.

Answer 2

It all looks right, good job