8builders completed the construction of a wall with a length of 15 meters and a height of 3 meters in 7 days and 7 hours, how many days needed for 4 builders to build the same wall

This is the concept of ratio and proportionality, we are required to find the total time taken to finish construction of a wall that 8 builders take 175 hours to build. To solve this question we proceed as follows;
Time taken by 8 builders=175 hours
Fraction of the wall completed by 8 builders in 1 hour= 1/175
Fraction completed by 4 builders in 1 hour will be:
4/8*1/175
=1/350
therefore time taken for 4 builders to finish the wall will be:
350 hours
=14 days and 14 hours