Answer :
Let L be the number of cookies of Lamar, S the number of cookies of Sang and E the number of cookes of Ester.
Since Lamar baked 12 more cookes than Sang, we can write the following equation:
[tex]L=S+12[/tex]Next, we have that Ester baked half as many cookies as Lamar, then we can write:
[tex]E=\frac{1}{2}L=\frac{1}{2}(S+12)[/tex]finally, we have that they baked 63 cookes altogether, then we have:
[tex]L+S+E=63[/tex]Using the values L = S + 12 and E = 1/2(S+12), we can find an equation and solve for S:
[tex]\begin{gathered} S+12+S+\frac{1}{2}(S+12)=63 \\ \Rightarrow2S+12+\frac{1}{2}S+6=63 \\ \Rightarrow\frac{5}{2}S+18=63 \\ \Rightarrow\frac{5}{2}S=63-18=45 \\ \Rightarrow S=45(\frac{2}{5})=\frac{90}{5}=18 \\ S=18 \end{gathered}[/tex]We have that Sang baked 18 cookies, then we can use this value to find how many cookies baked Lamar and Ester:
[tex]\begin{gathered} L=12+18=30 \\ E=\frac{1}{2}(12+18)=\frac{1}{2}(30)=15 \end{gathered}[/tex]therefore, Lamar baked 30 cookes, Sang baked 18 cookies and Ester baked 15 cookies