Jenny, eric and Boris sent a total of 79 text messages during the weekend Jenny sent 6 fewer messages than Erica Boris sent 3 times as many messages as Eric how many messages did they each send?

Lets say that J is for Jennys messages, B is for Boris' and E is for Erics (or Ericas?).

79 = J + B + E

J = E - 6

B = 3E

Since both Jenny's and Boris' number of text messages has some kind of relation to Eric's number of messages, we can say that:

79 = E - 6 (Jenny) + 3E (Boris) + E (Eric), so:

79 = E - 6 + 3E + E / combine like terms

79 = 5E - 6 / add 6 to both sides

79 + 6 = 5E / switch sides + combine like terms

5E = 85 / divide both sides by 5

E = 85/5

E = 17

So, Eric sent 17 messages. Lets get back to those equations we made for Jenny and Boris:

J = E - 6 = 17 - 6 = 11

B = 3E = 3 * 17 = 51

And we can check if it adds up: 51 + 11 + 17 = 79, which is what we were supposed to get.