What is the definition of an element​

A substance that cannot be broken down into simpler substances. An element is composed of atoms that have the same atomic number.

I hope it helps!

Explanation:

pure substance consisting only of atoms that all have the same numbers of protons in their atomic nuclei.

Explanation:

paraphrase it boi

a: 45.9 meters

b: 4.29 seconds

step-by-step explanation:

a: h(t)=1/2(-9.8)(3)^2+0(3)+90

h(t)=-4.9(3)^2+90

h(t)=-44.1+90

h(t)=45.9 meters

b: 0=1/2(-9.8)(t^2)+0t+90

0=-4.9t^2+90

-90=-4.9t^2

18.37=t^2

t=4.29 seconds

in the second question, the numbers aren't exact, but they're a close approximation.

tracks, burrows, eggshells, nests, tooth marks, or gastroliths