is 5 to 4 proportional to 35 to 28?

Yes it is, because:

5/4 X 7/7=35/28

Thanks, Guest....we could also see this by cross-product equality  [if cross products of two fractions are equal, the fractions themselves are equal ]

5/4  = 35/28   because

28 * 5 = 35 *4

140 = 140