Let us assume that the number of hours Issac worked = X hours
Since Ruby worked 4 hours more than Issac, the number of hours Ruby worked = X+4 hours
Now, Svetlana worked 4 times as much as ruby. So the number of hours Svetlana worked = 4*(X+4)
The total number of hours worked by all of them together is 92 hours.
So, we frame the equation as follows:
X + (X+4) + 4*(X+4) = 92
X + X + 4 + 4X + 16 = 92
6X + 20 = 92
6X = 72
X = 72/6 = 12 hours
So Issac worked for 12 hours
Ruby worked for X+4 = 12+4 = 16 hours
and Svetlana worked for 4*(X+4) = 4*(12+4) = 4*16 = 64 hours