Let
x--------> amount of erasers that Sari has
y--------> amount of erasers that Sam has
we know that
\(x=3y\)-------> equation \(1\)
\(x+y=28\)-----> equation \(2\)
Substitute equation \(1\) in equation \(2\)
\([3y]+y=28\\ 4y=28\\ y=28/4\\ y=7\)
find the value of x
\(x=3y\\ x=3*7\\ x=21\)
therefore
the answer is
Sari has \(21\) erasers
