兼ねる

私は勉強と遊びを兼ねている仕事につきたい。

I want to get a job that mixes work and play.

こういう事情ですから、残念ながら、せっかくのご招待をお受けいたしかねるのです。

As such is the case, I am sorry I can't accept your kind invitation.

今日は、ばーさんのお使いを兼ねて街で買い物。

Today I'm shopping in town as well as running an errand for my grandmother.