Answer:
30
Explanation:
Students performing in the school concert=40%
let the students in the class be x
hence 40% of the class=12
where 40%=40/100=4/10=2/5 and of means multiplication
(2/5)*x=12
multiplying both sides by 5/2
hence the equation becomes
x=12*5/2
x=60/2
x=30
so the total students in the class are 30