these are problems that can either be answered with a decimal or fraction, but the book only provides the fraction answer and i do decimal methods, so im worried i may have done something wrong...

numbers written like this: 1/2, 4/5

15.-2/3(6 - 2a)=6

multiply by -3/2

6-2a=-9

-6 from each side

-2a=-15

divide each side by -2

a=7.5

the book says the answer is 15/2 -----Okay. But what is 15/2? Is it 7.5?

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18.16=5(1-x)

distribute 5...

16=5-5x

-5 from each side..

11=-5x

divide each side by -5

-2.2=x

the book doesnt give an answer, so i'm even more worried about its correctness, lol.

One good way to check if your answer is correct is to plug/substitute your answer into the original equation. If your answer proves the equation true, then you have the correct amswer--even if the book's answer says otherwise. If your answer shows the original equation is false, then your answer is wrong.

So, here, your answer is x = -2.2. Substitute that into

16 = 5(1-x),

16 =? 5(1 -(-2.2))

16 =? 5(1 +2.2)

16 = 5(3.2)

16 =? 16

Yes, so, OK, your x = -2.2 is correct.

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20.n-4(1+5n)=-2

distribute -4...

n-4-20n=-2

add 4 to each side

n-20n=2

1n-20n=-19n

-19n=2

divide each side by -19

n=-0.105263158

book doesnt provide an answer, and the sheer length of the decimal has me worried, lol

Why not just n = -2/19 then?

After -19n = 2,

n = 2/(-19)

n = -2/19.

Check that by substituting it into the original equation. (It is correct, I checked.)

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and finally,

22.6m-3=10-6(2-m)

10-6=4 ----------------------this not correct. The -6 is connected to the (2-m). You cannot treat the -6 as separate.

Here is the continuation,

distribute -6,

6m -3 = 10 -12 +6m

subtract 6m from each side,

-3 = -2

Whoa, no more unknown?

Besides, -3 is not equal to -2 either.

So, the given equation has no solution.

6m-3=8-4m

add 4m to each side

10m-3=8

add 3 to each side

10m=11

divide each side by 10...

m=1.1

the main thing im worried about here is that the teacher said between problem 17 and 22 there was 1 problem with 'all numbers' as an answer and 1 problem with 'no solutions' as an answer. i got the all numbers one, but the answers to all the others, unless i did something wrong, are

17. -2=z

18. 2=h

19. all numbers

20. r=-5

21. x=-15

22. m=1.1

so, 22 seems the most likely to have been the one i made a mistake in, due to the fact all the others have solid non-decimal answers.

thanks in advance.