An unknown radioactive element decays into non-radioactive substances. In 900 days the radioactivity o sample decreases by 49 percent . (a) What is the half-life of the element? half - : ( days) Round to two decimal places . How long will it take for a sample of 100 mg to decay to 51 mg

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step-by-step explanation:

x = -3

y = -18

step-by-step explanation:

to solve by substitution, substitute one variable and solve for the other. then substitute again to find the remaining variable.

x-1/3(3x-9) = -3 since y=3x-9 substittute y.

x-1/3(3x-9)=-3

x + x +3 = -3

2x+3=-3

2x+3-3= -3-3

2x=-6

x=-3

substitute again into y=3x-9

y=3(-3)-9

y=-9-9

y=-18

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step-by-step explanation: