Algebra question . helpppp

a 1-oz mouse takes about 16 times as many breaths as does a 3-ton elephant. if the two animals take a combined total of 170 breaths per minute, how many breaths does each breaths does each take during that time period ?

mouse :
elephant :


if a number is subtracted from 8 and this difference is tripled, the result is three times the number. find this number and you will learn how many times a dolphin rests during a 24-hour period .

answer : 3

x + 16x = 170
x = 10, the number of breaths for the elephant
16x = 160, the number of breaths for the mouse

3(8-x) = 3x
6x = 24
x = 4 for the dolphin, not 3

Let X = the elephant's breaths/minute
Let Y = the mouse's breaths/minute

X + Y = 170
Y = 16 * X

Using substitution, we get:

X + 16X = 170

Add like terms to get:

17X = 170

X = 10, and Y = 16 * 10 = 160

So the elephant takes 10 breaths per minute, and the mouse takes 160 breaths per minute.

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For the dolphin problem:
Let X = the unknown number
3 * (8 - X) = 3X
Dividing both sides by 3 to get rid of the 3 on the left, you get:
8 - X = X
Add X (from the left side) to both sides, you get:
8 = 2X
Dividing both sides by 2, you get:
4 = X

Here's how I would do it, which is probably not the way you're teacher would want...
If the mouse takes sixteen times the breaths as the elephant, there are 17 parts total. 170 divided by 17 is 10. Therefore, the elephant takes ten breaths and the mouse takes 160. To check, ten times 16 is 160. The weight is irrelevant.
Algebraically, I believe you would have to use a system of equations, but don't quote me on that because it's been a long time for me.
Here's a general tip: If you get a whole number or the numbers just seem to work out perfectly, like it did here, you're probably right. If you get a ten digit decimal when all the other answers are whole numbers, you're probably wrong.