Answer:
I'm not so sure about this one so sorry if this is wrong
Step-by-step explanation:
Answer: 
-3 times the square root of 5
=============================================
Explanation:
Let 
Replace all the root 5 terms with x and we go from

to

From here, combine like terms to get

and the last thing to do is replace the x with sqrt(5)

Meaning that,


I think you got confused with the 50 and 90.
Read my NOTE there it will surely help you answering other questions like this
Answer:
Half-life of the goo is 49.5 minutes

191.7 grams of goo will remain after 32 minutes
Step-by-step explanation:
Let
denotes initial and final mass.

According to exponential decay,

Here, t denotes time and k denotes decay constant.

So, half-life of the goo in minutes is calculated as follows:

Half-life of the goo is 49.5 minutes

So,

Put 

Put t = 32 minutes
