Answer:
Step-by-step explanation:
100 + 100 + 6x + 6 + 12x - 8 = 360 Equation. Collect like terms.
198 + 18x = 360 Subtract 198 from both sides
18x = 360 - 198
18x = 162 Divide by 18
x = 162/18
x = 9
Answer:

Step-by-step explanation:
we are given half-life of PO-210 and the initial mass
we want to figure out the remaining mass <u>after</u><u> </u><u>4</u><u>2</u><u>0</u><u> </u><u>days</u><u> </u>
in order to solve so we can consider the half-life formula given by

where:
- f(t) is the remaining quantity of a substance after time t has elapsed.
- a is the initial quantity of this substance.
- T is the half-life
since it halves every 140 days our T is 140 and t is 420. as the initial mass of the sample is 5 our a is 5
thus substitute:

reduce fraction:

By using calculator we acquire:

hence, the remaining sample after 420 days is 0.625 kg
I think the correct answer is D
Answer:
$135
Step-by-step explanation:
Paperback=$4.75
Hardcover=$11.50
Multiply 4.75 and 20=95
Multiply 11.50 and 20=230
Subtract 230 and 95=135
so it would be $135