I am a halogen. I am a gas at room temperature. And of those halogens that are gases, I am the heaviest of the two
Who am I?

Chlorine

Explanation:

The two halogens that are gases at room temperature are Fluorine and Chlorine, as they are at the top of the group.

The heaviest of the two is chlorine as the density of Fluorine is 1.696g/dm3 and the density of Chlorine is 3.214g/dm3 so chlorine will weigh more with the same amount.

Hope this helps, let me know if you have any questions :)

linda: 3 ; laura: 15

step-by-step explanation:

note that linda + laura's age is 18, and that linda is 12 years younger than her sister.

let "linda" = x , "laura" = y:

x + y = 18

x = y - 12

first, plug in y - 12 for x in the first equation:

(y - 12) + y = 18

simplify.

2y - 12 = 18

isolate the variable (y). note the equal sign, what you do to one side, you do to the other. do the opposite of pemdas. first add, then divide.

2y - 12 (+12) = 18 (+12)

2y = 18 + 12

2y = 30

(2y)/2 = (30)/2

y = 30/2

y = 15

next, plug in 15 for y in the second equation (the other equation would work too).

x = y - 12

x = (15) - 12

x = 3

linda's age is 3, laura's age is 15.

~

the answer would be c