Answer:
The number of messages sent by Melissa was 25
The number of messages sent by Keith was 60
The number of messages sent by Chau was 15
Step-by-step explanation:
Let
x ----> the number of messages sent by Melissa
y ----> the number of messages sent by Keith
z ----> the number of messages sent by Chau
we know that
[tex]x+y+z=100[/tex] ------> equation A
[tex]z=x-10[/tex] -----> [tex]x=z+10[/tex] ----> equation B
[tex]y=4z[/tex] -----> equation C
substitute equation B and equation C in equation A
[tex]z+10+4z+z=100[/tex]
Solve for z
[tex]6z+10=100[/tex]
[tex]6z=100-10[/tex]
[tex]6z=90[/tex]
[tex]z=15[/tex]
Find the value of x
[tex]x=15+10=25[/tex]
Find the value of y
[tex]y=4(15)=60[/tex]
therefore
The number of messages sent by Melissa was 25
The number of messages sent by Keith was 60
The number of messages sent by Chau was 15