Melissa is represented by variable m.
Josh is represented by variable j.
Chau is represented by variable c.
m+j+c= 148
c=4m
j=m+10
Substitute for c and j for the first equation.
m+(m+10)+4m=148
6m+10=148
6m=138
m=23
Plug the known m value in
j=23+10
j=33
c=4(23)
c=92
Final answer: Melissa=23 messages, Josh=33 messages, Chau=92 messages