My teacher never taught us this, but expects us to know

I'll do problem 77 to get you started

Point slope form is this general equation

y - y1 = m(x - x1)

with m as the slope and (x1,y1) as the point the line goes through. In this case, m = -4 and (x1,y1) = (-2,9)

Plug those values into the equation to get...

y - y1 = m(x - x1)

y - 9 = -4(x - (-2))

y - 9 = -4(x + 2) see note 1

y - 9 = -4x - 8

y = -4x - 8 + 9

y = -4x + 1 see note 2

note 1: If your teacher wants the answer in point slope form, then you stop on this line. Otherwise, keep going

note 2: This is in slope intercept form y = mx+b with m = -4 as the slope and b = 1 as the y intercept

i don't know

step-by-step explanation:

ending amount = beginning amount / (2^n)

where "n" = number of half-lives (or elapsed time / half-life)

ending amount = 50 mg / (2 ^10 / 5.3)

ending amount = 50 mg / (2 ^ 1.8867924528)

ending amount = 50 m / 3.6981210597

ending amount = 13.5203794557 mg

or about 13.5 mg remain

source: