A Math teacher was conducting an Algebra lesson and gave the class a riddle to solve by using an equation to find the unknown value. After sometime the teacher asked the students to put up hands of those who got the correct answer 10 for the riddle. As no one raised hands, the teacher did the question on the board. He used x as the unknown quantity and computed the equation, then solved the riddle. He walked around the class checking the books to findout what difficulties they had in getting 10 as the answer.Finally he came accross a student who got the correct answer 10 but had not raised her hand. The teacher asked " why didn't you put up your hand"? . The girl replied " Sir I did not use x, but I used a instead. This is really a true incident.