You have to figure out the highest common factor of each set of values:
9a + 21 = 3(3a + 7)
21b - 49 = 7(3b - 7)
54 - 6c = 6(9 - c)
8a + 32b = 8(a + 4b)
4p + 28q + 8r = 4(p + 7q +2r)
84a - 36b -12c = 6(14a - 6b - 2c)
6p + 9q + 15r = 3(2p + 3q + 5r)
18s - 30t + 54u = 6(3s - 5t + 9u)
Hope this helps :)
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
Answer:
300,000,000 or three hundred million
Step-by-step explanation:
Answer:
I think it is D
Step-by-step explanation: