For this case we have the following equations:
2x - 3y = 1
2x + 3y = 2
When adding both equations we observe that:
Sentence 1: we have an equation of a variable, which in this case will be x. We can clear the value of x.
Sentence 2: Knowing the value of x, we can substitute in any equation and find the value of y.
Sentence 3: The value of x and y represents the point of intersection of both lines (x, y).
It is 800 because the 4 can not tell the what to do so that it is
For a half- life, the formula is
A(t) = A0(0.5)^( t / t_0.5)
where A(t) is the amount of substance at time t
A0 is the initial amount of subtance
t_0.5 is the time it will reduce its amount to half
t is the time
substitute the given to the formula
A(t) = 100(0.5)^( t/6 )
so the decay factor is 0.5^( t/6 )