Answer:
6 weeks
Step-by-step explanation:
Set up a proportion where x is the amount of time with 12 pupils:
= 
Cross multiply and solve for x:
4x = 24
x = 6
So, it will take 12 pupils 6 weeks to complete the job.
Percent means parts ot of 100
10%=10/100=1/10
'of' means mutily
10% of what=14
1/10 times what=14
mutiply both sides by 10
what=140
the number is 140
(-6)-(+8)-(-12)
-6-8+12
-14+12
-2