Question 1161079
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The solution by the other tutor is fine....<br>
But solving a problem like this is nearly always much easier if you take the time to set it up to be solved using a single variable instead of three.<br>
The given information compares the numbers of messages sent out by both Dan and Kevin to the number sent out by Raina.  So let your variable be the number sent out by Raina:<br>
x = number sent out by Raini
2x = number sent out by Dan (twice as many as Raina)
x+8 = number sent out by Kevin (8 more than Raina)<br>
Then write a single equation in the single variable that says the total number of messages was 104:<br>
{{{(x)+(2x)+(x+8) = 104}}}<br>
Solving that single equation is basic algebra -- much easier than working with three equations and three unknowns.<br>