Presuming the 4-line means the student E-mail is composed of 4-lines, to be able to determine how many characters were on each line, let's divide the total characters that a student E-mail contained by 4.
We get,
[tex]\text{ Characters per Line = }\frac{Total\text{ Characters}}{4\text{ Lines}}\text{ = }\frac{250\text{ Characters}}{4\text{ Lines}}[/tex][tex]\text{ = }\frac{250}{4}\text{ = 125 = 125 Characters per Line}[/tex]Therefore, the Student E-mail of 250 Characters in 4 lines must have 125 Characters per Line.