The measure of angle FEB is 77°.
Reminder - After some quick research, we conclude that user made a typing mistake on question. The correct form is:
"If EF bisects angle CEB, angle [tex]CEF = 7\cdot x + 21[/tex] and angle [tex]FEB = 10\cdot x - 3[/tex], find the measure of FEB."
A Bisector is a Line which divides an Angle into two equal Sections. Given that Angles CEB and FEB have the same Measure, we have the following identity which is solved for [tex]x[/tex].
[tex]7\cdot x + 21 = 10\cdot x - 3[/tex]
[tex]3\cdot x = 24[/tex]
[tex]x = 8[/tex]
And then we find the Measure of the Angle FEB (Angles are measured in sexagesimal degrees):
[tex]FEB = 10\cdot x - 3[/tex]
[tex]FEB = 10\cdot (8) - 3[/tex]
[tex]FEB = 77^{\circ}[/tex]
The measure of angle FEB is 77°.
Please see this question related to Bisectors: https://brainly.com/question/12896755
