Question

http://prntscr.com/9r5b0n
I finished my test, and I got two answers incorrect. This was one of them. I did 2a-20.4=a+1.6 and got 22 and
a-3.5=18.5 and got 22. So, I timed 22 by 4 and got 88. Though, the answer was 84.2. I'm not sure what I did wrong.
http://prntscr.com/9r5c36
This was the other.
For number 7 I got 4, but it turned out to be 11.
I set my equation up as 2x+2(3+2x)=30 and got 6.
The answer is 11. I'm not sure what I did wrong.

Answer 1

I got four as in I chose 4 because I gave up, but I calculated six.

Answer 2

Alright for the first problem, let me see here: (I came out with left and right at 23.6, up and down at 18.5, and 'a' equaled '22'.)
Okay, the problem with your first one is that you executed it incorrectly, you did everything correctly, but this is measuring for the actual sides, in other words:
You know 'a' is 22, so:
1. a - 3.5 = ? -> 22 - 3.5 = 18.5
2. 2a - 20.4 = ? -> 2(22) - 20.4 = ? -> 44 - 20.4 = 23.6
3. a + 1.6 = ? -> 22 + 1.6 = 23.6
4. 18.5 = 18.5
Add the values that you acquired(not just 'a') together:
23.6 + 23.6 = 47.2
18.5 + 18.5 = 37.0
Now add those values like you would for the perimeter:
94.2
Are you sure for the first problem your answer wasn't 94.2? Otherwise I'm lost without the '10'...

Answer 3

@ghostgate
Thank you. I now see the error in problem 5.

I'm lost at your question at the bottom. 94.2?

Answer 4

I got 94.2 as the answer, and you said that you put '88' by multiplying 'a'(22) 4 times followed by that their answer was 84.2, but I came out with 94.2, my question was is that was the answer 84.2 or 94.2?
Also, you're welcome! ;) - I'm trying to solve your second question.

Answer 5

@Ghostgate

Oh, why, yes that was the answer! When I added 47.2 and 37.0 I got 84.2.

Answer 6

Oh man, I did basic math wrong, haha. xD - 47.2 + 37.0 = 84.2 not 94.2. Man... I feel stupid now. Lol

Answer 7

@Ghostgate you're fine sweetie. I'm grateful you're even helping me!

Answer 8

I'm not sure if this is correct due to how for problems like your second one I use the 'trial and error' system and plug numbers in till one fits. Lol - However, I came up with a way that solves your problem, but I have no way if it will solve future ones:
x is 'AB', and 'AD' is 3 more than twice 'AB', so:
x + 2x + 3 = 30
3x + 3 = 30 - Does that make more sense? If you use the mathematical steps you can solve the problem to get what they wanted, where 'AB' is 4, then after doubling it and adding a 3 you get 11, which allows you to find out what 'BC' is.
Does that make sense? I hope so, also the reason it wasn't 4 is due to how you're solving for 'BC' not 'AB', 'AB' is 4. See: