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
(x+1)-(-2x-5)
=x+1+2x+5
=3x+6
=3(x+2)
4 x p - 9 = 3 x p + 6
Hope it helped
Answer:
An equation represents the number of pieces of lasagna that are left after dinner is 
Step-by-step explanation:
Each piece of Lasagna is 1/6 of the pan
Let x be the number of pieces left
So, x pieces is
of the pan
We are given that After dinner 2/3 of a pan of lasagna is left.
So, 

x=4
So, Number of pieces left = 4
Hence An equation represents the number of pieces of lasagna that are left after dinner is 
Three times as long of 20 square meters would be 60
you can do 20×3 to get 60.