Answer:Amanda sent 7 messages
Bob sent 51 messages
Scott sent 17 messages
Explanation:
Let x represent the number of messages that Amanda sent.
Let y represent the number of messages that Bob sent.
Let x represent the number of messages that Scott sent.
Amanda bob and Scott sent a total of 75 messages over the weekend. This means that
x + y + z = 75 - - - - - - - - - - - - - 1
Bob sent 3 times as many than Scott. This means that
y = 3z
Amanda sent 10 fewer messages than Scott. This means that
x = z - 10
Substituting y = 3z and x = z - 10 Intl equation 1, it becomes
z - 10 + 3z + z = 75
5z = 75 + 10 = 85
z = 85/5 = 17
y = 3z = 3 × 17 = 51
x = z - 10 = 17 - 10
x = 7