The difference between the heights of your chair and your desk is -10 1/4 inches. the height of your desk is 29 3/4 inches. what is the height of your chair?

Since you said the height of your chair and you desk, chair would go first when subtracting.
C= chair
c - 29.75 = -10.25
 + 29.75  = + 29.75
c= 19.5
So, you chair is 19.5 (19 1/2) inches tall.

the law of definite proportions states samples of a compound will always contain the same proportion of elements by mass. in other words, a given compound will always contain the same elements in the same proportions by mass.the law of multiple proportions states when two elements combine with each other to form more than one compound, then the weights of one element that combine with a fixed weight of the other are in a ratio of small whole numbers.