Answer:
Amount of Niobium-91 initially
= 300/91 =3.2967mol
2040 years = 3 ×680 = 3 half-lives
therefore, amount left = 0.4121mol
mass of Niobium-91 remaining = 0.4121 ×91 =37.5g
Please give brainliest
Hello.
First of all, let the number be t.
8 times t can be written like this:

Notice that the number is before the variable and the times sign (×) is not there.
We can write it as 8×t, but we usually write it as 8t.
The sum of means we add:
8t+21
Now, "less than" is "<" :

Therefore, the answer is

I hope it helps.
Have a nice day.

The main formula of a spherical surface area is SA= 4 x Pi x r²
the circumference is C= 19cm =2 Pi r, so r = C/ 2Pi = 19 / 6.28 =3.02cm
so the surface area can be found by computing
SA= 4x 3.14x 3.02² =114.5, the nearest square centimeter is <span>A) 114 cm^2</span>
Answer:
Gaming Functions
Step-by-step explanation:
I think your teacher is implying for you to explain the function and the "works" behind the game. Maybe talk about the game's programming or the way it's overall structured?