This is all I need because its 55% of my grade on this practice, please help ty.

, , , ,

Step-by-step explanation:

First question:

He starts with 18, gains 2 every week, and needs 42. This means the equation is .

Second question:

He starts with 2, gains 18 every week, and needs 42. This means the equation is .

Third question:

It starts with 42, loses 2 every day, and needs 18. This means the equation is .

Fourth question:

Each friend has a total bill of 18+x, there are 2 friends, and they need 42. This means the equation is .

The only answer left is , so that's the answer to the fifth problem.

the answer is: d) o, f, and kr.

atomic radius of bromine (br) is 114 pm.

atomic radius of oxygen (o) is 73 pm.

atomic radius of fluorine (f) is 72 pm.

atomic radius of krypron (kr) is 112 pm.

the atomic radius of a chemical element is a measure of the size of its atom.

the atomic radius varies with increasing atomic number, but usually increases because of increasing of number of electrons.

the atomic radius decreases across the periods because an increasing number of protons, because greater attraction between the protons and electrons.