If 3 is added to a number and the sum is tripled, the result is 21 more than the number. Find the number

9

Step-by-step explanation:

If 3 is added to the number: x + 3

b) ...and the sum is tripled..

"The sum" is "x + 3" so: 3(x+3)

c) ...the result is 27 more than the number.

27 more than the number is x + 27

d) Put it all together:

3(x + 3) = x + 27

Solve for x:

1) Distribute the left side of the equation:

3x + 9 = x + 27

2) Subtract x from each side of the equation:

2x + 9 = 27

3) Subtract 9 from each side of the equation:

2x = 18

4) Solve for x:

x = 9

Check:

1) x = 9

2) 3(x + 3) = x + 27

3) 3 ([9] + 3) = [9] + 27

4) 3(12) = 9 + 27

5) 36 = 36

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.

it shoild be o

step-by-step explanation: