Answer: There were 10 students in the class on the first day.
Step-by-step explanation:
Let x be the number of students of the first day.
Given: A college writing seminar increased its size by 50 percent from the first to the second day.
i.e. Number of students on second day = (Number of students on first day)+(50% of Number of students on first day)
= x +50% of x
= x+0.50x
= (1.50)x
=1.50x
Since, it is given that the total number of students in the seminar on the second day was 15.
i.e. 

Hence, there were 10 students in the class on the first day.
Math is used in construction everywhere.Math is used in construction to measure parts, how many feet, inches, etc. to do and how high to go up.A great example is in the scaling of blueprints, where an architect creates a scale model of the building so that it can fit on paper.