Determine whether the two expressions are equivalent. If so, tell what property is applied.
If not, explain why.
18. 18 x 17 18
19. 8 + 1.2 = 1.2 + 8
20. 10 = (8 - 4) = (10 - 8) dived by 4

The graph and table shows the relationship between y, the number of words jean has typed for her essay and x, the number of minutes she has been typing on the computer. according to the line of best fit, about how many words will jean have typed when she completes 60 minutes of typing? 2,500 2,750 3,000 3,250

Acertain volume of water contains 100000 hydrogen atoms and 50,000 oxygen atoms how many hydrogen atoms are in a volume of water containing 4 million oxygen atoms

Set $r$ is a set of rectangles such that (1) only the grid points shown here are used as vertices, (2) all sides are vertical or horizontal and (3) no two rectangles in the set are congruent. if $r$ contains the maximum possible number of rectangles given these conditions, what fraction of the rectangles in set $r$ are squares? express your answer as a common fraction.