Let x, y, and z be the number of calls Kira received during the first, second, and third day, respectively. Therefore, the equations are
[tex]\begin{gathered} x+y+z=54 \\ x=y-10 \\ z=2y \end{gathered}[/tex]
Solve the system of equations as shown below
[tex]\begin{gathered} \Rightarrow x+y+z=x+(x+10)+2(x+10)=4x+30 \\ \Rightarrow4x+30=54 \\ \Rightarrow4x=24 \\ \Rightarrow x=6 \end{gathered}[/tex]
Use the value of x to find y and z,
[tex]\begin{gathered} x=6 \\ \Rightarrow6=y-10\Rightarrow y=16 \\ and \\ z=2y=2*16=32 \end{gathered}[/tex]
Therefore, the answers are:
First evening: 6 calls
Second evening: 16 calls
Third evening: 32 calls