-7x-3x+2=-8x-8 | combine like terms
-10x+2=-8x-8 | add 8x
-2x+2=-8 | subtract 2
-2x=-10 | divide by -2
x=5
Answer: 
Work Shown:

Note that (h,k) = (2,-3) is the center and r = 6 is the radius. The last line is not expanded out using the FOIL rule because its common practice to leave it in
form. This form allows the reader to quickly determine the center and radius (rather than have to do a lot of algebraic steps before hand).
Answer:
On the 7th day.
Step-by-step explanation:
The mold doubles, so on the 7th day, the mold would be half-there.
I used the 8th day's description to figure this out.
Answer: The 80ml is the best deal
Step-by-step explanation:
Bc the half price of 45 is 22.5 so 45 + 22.5 equals $67.50 and the 80ml would equal 55.
Therefore the 80ml one is cheaper than the 50ml
8.77 x 10^1 i believe but would double check