The Half-life of a certain substance is 20 mins. You start with 45 mg of the substance
(a) Set up an equation to model how much of the substance you have.
(b) How much of the substance would you expect to have in 4 hours?
(c) How long until there is 1 gram of the substance left?

Step-by-step explanation:

Let   denote the half life of our substance to be our time, is mass at time t and as initial mass. Our half life equation can be expressed as:

from which we can obtained mass at any given time.

b. From our equation above,

we can convert our t into mins as

We then substitute value into the equation

Hence mass after 4hrs is

c. We can set our final mass to  then substitute in the equation

. Substitute

Hence time until mass is 109.83 minutes

x = 10.1

step-by-step explanation:

all of the angles of a tirangle add up to 180º

180 - 65 = 115 (since we already know the value of one angle)

(2x + 7) + (8x + 7) = 115

(combins like terms) 10x + 14 = 115

(isolate the variable subtract 14 from both sides): 10x = 101

(find the variable divide both sides by 10): x = 101/10

x = 10.1

answer: options?

step-by-step explanation: