The function gives the mass, m, of a radioactive substance remaining after h half-lives. Cobalt-60 has a half-life of about 5.3 years. Which equation gives the mass of a 50 mg Cobalt-60 sample remaining after 10 years, and approximately how many milligrams remain?

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step-by-step explanation:

a

(6r + 7) + (13 + 7r) ( remove brackets and collect like terms )

= 6r + 7 + 13 + 7r

= 13r + 20

b

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13 - r - 1 + r

= 12 - r

c

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= - 8 - r + 2r - 4

= - 12 + r

d

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= 7r - - - 6r

[-   - = - - = - ]

= r -