0.9 + 0.02 + 0.004 is the expanded form of 0.924, it is just taking apart each place in the number.
Answer: 9.70%
Step-by-step explanation:
The formula to find the percentage error is given by :-

Given : Actual mass of zinc oxide used by pharmacist = 28.35 g
Estimated mass of zinc oxide used by pharmacist =31.1 g
Now, 
i.e. 
i.e. 
Hence, the percentage of error on the basis of the desired quantity.= 9.70%
A. 6x-y=1 can go to 6x-y-1=0 and then 6x-1 = y
First move the 2n over to the other side by subtracting it
so
4n=-8
then divide 4n by 4 and do the same to the other side
so
n= -8/4
n= -2