15/40 = 5/8
cross multiply
(15)(8) = (40)(5)
120 = 200...incorrect...so it is not a true proportion
little tip : proportions are nothing but equivalent fractions...15/40 is not equivalent to 5/8.....now if it would have been 15/40 = 3/8 , since these are equivalent fractions, this would have been a true proportion
