Upon formation of an equation from a given pattern, we know how the variables in the patter are related. Using the equation, we can find the value of one of the missing variables if the rest are known and also predict the values of the pattern at given conditions.
An example:
y = 2x + 5
if we are to predict the value of y at x = 3, we simply substitute 3 into x
y = 2(3) + 5
= 11
I'm assuming you meant shirts instead of shorts for the older brother.
1/6 + 3/6 = 4/6
4/6 of the shirts belong to his brothers
(or 2/3 if you simplify the fraction)
For the half-life of a certain substance, the equation that would best represent the scenario is,
At = Ao(0.5^t/n)
where At is the amount at any time t, Ao is the original amount, and n is half-life. Substituting the known values,
At = (220 mg)(0.5^(396/72)
At = 4.86 mg
Thus, after 396 days, there will only be 4.86 mg of Terbium-160.
