Find the scale factor of a construction plan if the scale is 0.75 centimeters = 3 meters.

Typically a plan is much smaller in size than is the object or structure to be built.  Converting 0.75 cm into meters and then dividing the result into 3 meters will give you a positive scale factor greater than 1.

Note that we can convert 0.75 cm into m by multiplying 0.75 cm by the conversion factor

1 meter

100 cm

Please do this now.  
Next, divide your result into 3 meters to obtain the scale factor.

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.