Here are the completed statements using 'as ... as' or 'not as ... as':
Joe isn't as old as Tony. (old)
This sentence compares Joe and Tony's ages using "not as....as". Joe is not as old as Tony because Joe is sixteen while Tony is seventeen.
I am not as tall as my sister. (tall)
This sentence uses "not as...as" to compare height. Since I am 165 cm and my sister is 170 cm, I am shorter than my sister.
Tokyo is as cold as Moscow. (cold)
This sentence shows that both Tokyo and Moscow have the same temperature, -5°C, using "as...as".
The black shoes are not as expensive as the red shoes. (expensive)
Here, we are comparing the prices of the two pairs of shoes. The black shoes cost $20, which is less expensive than the red shoes' cost of $25, so we use "not as...as".