Amanda bob and Scott sent a total of 75 messages over the weekend. Bob sent 3 times as many than Scott. Amanda sent 10 fewer messages than Scott. How many messages did they send

Let the total number of messages sent by Scott = S

Bob sent =3S

Amanda sent =S - 10

S + 3S + S - 10 =75, solve for S

5S =75 + 10

S =17 - messages sent by Scott

17 x 3 =51 messages sent by Bob

17 - 10 = 7 messages sent by Amanda. So that:

17 + 51 + 7 =75 - total number of messages sent by all.