Answer:
Let the number of girls be x.
Given condition: Total number of student in a class is 42 students and the number of boys is 12 fewer than twice the number of girls.
As per the given condition" the number of boys is 12 fewer than twice the number of girls"
twice the number of girls means 2x
12 fewer than twice the number of girls which means 2x -12.
Therefore,
the number of boys = 2x-12
Total number of students in class = number of boys + number of girls
⇒ 42 = 2x -12 +x
Combine like terms on RHS,
42 = 3x -12
Add 12 to both sides in above equation;
42+12 = 3x-12+12
Simplify:
54 = 3x
Divide by 3 to both sides we have;
Simplify:
18 =x or
x = 18
therefore, the number of girls be x = 18.