Answer:
9
Step-by-step explanation:
57 + 32x equals 435 - 10x
42 x equals 378
x equals 9
Let p be the prize of a pen and m the prize of a mechanical pencils. If you buy six pens and one mechanical pencil, you spend 6p+m. We know that this equals 9, because you get 1$ change from a 10$ bill.
Similarly, if you buy four pens and two mechanical pencils, you spend 4p+2m, which is 8$, because now you get a $2 change. Put these equation together in a system:

Now, if you multiply the first equation by 2, the system becomes

Subtract the second equation from the first:

Plug this value into the first equation to get

Answer:
-1
Step-by-step explanation:
The mean is the sum of all values divided by the amount of values.
We take the sum of all the numbers:
-3 + -8 + 12 + -15 + 9
-11 + 12 + -15 + 9
1 + -15 + 9
10 + -15
-5
We then divide the sum by how many number we have (we are given 5 numbers):
-5/5 = -1
Therefore, our mean is equal to -1.
Answer:
12
Step-by-step explanation:
4 / sqrt {9}
4(3)
4 x 3
12