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Nordic combined is a sport that combines two events: ski jumping and cross-country skiing.
Literal
Nordic-combined [topic-は], ski-jumping [and-と] cross-country-skiing [genitive-の] 2 [genitive-の] events [object-を] combining is-conducted.
A sports definition. 行われる is the passive of 行う ('to conduct, perform'), commonly used for events being 'held' or 'conducted.' The pattern ~を組み合わせて行われる ('is conducted by combining X') uses the て-form of 組み合わせる (combine, pair up) as a means-of clause. Note the noun phrase structure: ２つの競技 ('two events') is the object being combined, and the modifier スキージャンプとクロスカントリースキーの specifies which two. The Nordic combined is a winter Olympic event that pairs these two traditional Nordic disciplines.