Why no y in correct answer

Question

20,354 = twenty thousand three hundred and fifty four= veinte mil trescientos cincuenta y cuatroNotice how in Spanish we need toadd "y" between the tens and the units (cincuenta y cuatro). Three thousand six hundred and six.(HINT: Write the number in letters in Spanish (not digits))Three thousand six hundred and six.(HINT: Write the number in letters in Spanish (not digits))Three thousand six hundred and six.(HINT: Write the number in letters in Spanish (not digits)) But there’s no y in this correct answer: Tres mil seiscientos seis

Answer

Hola Shirley
I am not 100% sure which question you're referring to as there is no mention of a specific one, but looking at all the test-questions we have for this topic I guess you may be referring to the lack of "y" on one of the numbers that don't have "tens", therefore you don't need the "y". For example:
Three thousand six hundred and six:
Tres mil seiscientos seis
 
Twenty five thousand three hundred and five:
Veinticinco mil trescientos cinco
 
If we had tens as well, then you'd need the "y", for example:
 
Twenty five thousand three hundred and THRITY five:
Veinticinco mil trescientos TREINTA Y cinco
 
Saludos
Inma

Answer

Muchas Gracias Inma! Shirley.