Learn Spanish (Spain): En el Congreso hay trescientos cincuenta diputados. - There are three hundred and fifty MPs in Congress.

In Spanish, you only use y between tens and units, such as in treinta y cinco. When connecting hundreds and tens, you just place them next to each other, making it trescientos cincuenta.

Does the word trescientos change its ending here?

Yes, the hundreds in Spanish (from 200 upwards) must agree in gender with the noun they count. Because diputados is masculine, we use trescientos. If it were a feminine noun like personas, it would be trescientas cincuenta.

What does Congreso specifically mean in this context?

In Spain, el Congreso refers to the Congreso de los Diputados, the lower house of the Spanish parliament. It is the equivalent of the House of Commons in the UK or the House of Representatives in the US.

Why translate diputados as "MPs" rather than "deputies"?

While "deputies" is a direct translation, English speakers more commonly use "MPs" (Members of Parliament) to refer to elected national representatives. In Spain, a diputado is exactly that: a member of the lower house of parliament.