If a 8 by 10 picture is enlarged by a scale factor of 3/4, what would be the new dimensions? What about a scale factor of .5?

The scale factor of (3/4) would mean that each dimension would be (3/4) of what it was before.....

So.....

 8 x 10  =   (3/4)8 x  (3/4)10   = 6 x 7.5

And .5 would be

(.5)8 x (.5)10 =  4 x 5