3. Being Motzi another person by a before blessing over food:

See Chapter 4 Halacha 2C and 5 for the full details of this subject!

The custom is for every person to say their own blessing by all foods and drinks other than bread and wine, and not fulfill their obligation with the blessing of others.[1] However, from the letter of the law, one can be Yotzei a before blessing from another if they are in a state of Kevius and both had intention to be Yotzei Motzi with the blessing. However, this only applies if the person saying the blessing is personally obligated in a Bracha Rishona. However, if he is not personally obligated in a Bracha Rishona then he may not recite a before blessing on behalf of another person who is eating a food or beverage, even if the other person does not know how to say the blessing themselves.[2] Likewise, if they are not Kavua together, one cannot be Yotzei the blessing with another.[3]

• Example: Two friends, Yaakov and Moshe, sit together to eat a sandwich. Yaakov recites the blessing out loud, both intend for this to cover them, and both are eating. In this case, Moshe fulfills their obligation. If they weren’t eating together or didn’t share intent, each would need to say their own blessing.

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[1] Admur 213:1; Implication of Admur 167:17

[2] See Admur 167:23; 197:6; 213:3; 273:6; Michaber 167:19; 213:2; Rosh Hashanah 29a; Encyclopedia Talmudit Erech Brachos Vol. 4 p. 344-350

[3] See Admur 167:15-17; 193:1-2; 213:1