Answer:
(a) We will form an equation of line from the points given (6,10) and (2,15)
Using:
On substituting the values in the formula above we will get the required equation of line.


On simplification we will get:

(b) We need to tell at day 0 put x=0 in above equation:


Anika worked for 70 hours on the set up crew on the day the fair arrived at the fairgrounds day 0.
Now, we need to tell decrease per day which is equal to the slope of line
To find the slope compare the equation with general equation which is y=mx+c where m is slope
Here, in 
which is the decrease per day.
Really hope this proves useful to you, any further questions please ask :)
So... the radiator has 15 liters of 70% antifreeze.. but needs an 80% antifreeze
well, so, you need to drain some and put some with higher percentage, seems to be, you will end up at the same 15 liters, possible the radiator's capacity, of 80% antifreeze
so, the same amount going out, of 70% is the same amount going in, of 100% antifreeze
now.. let's use the decimal format for the percents, or 70% is 70/100 or 0.7 and so on

so.. let's subtract, from the current solution, 0.7x and add 1x or x, our antifreeze concentration amount, should be 12 though
10.5 - 0.7x + x = 12
solve for "x"

1) Since in the USA 8 x 10 ^9 messages are sent every month, that means that approximately 8 billion messages are sent.
2) We can Prime factorize it:
Note that on the right side we've picked only prime numbers. In this case, 2 and 5.
So we can rewrite 8 x 10^9 as prime factors.

3) Hence, the answer is: