割引

How it works

This is just a noun phrase plus a copula — no verb needed. 二十パーセントにじゅっパーセント (twenty percent) stacks straight onto 割引わりびき (discount) to mean "a twenty-percent discount," and the polite です (is) at the very end states it as a fact. Japanese builds the amount before the thing it modifies, so the number leads and 割引わりびき (discount) follows.