Let Issac work for x hours, and Ruby works 8 hours more than of Issac, so Ruby work for [tex] (x+8) [/tex] hours.
And Svetlana worked four times of Ruby, therefore Svetlana worked for
[tex] 4(x+8) hours [/tex]
And total hours they worked together is 136. That is
[tex] x+x+8 + 4(x+8) = 136 \\ x+x+8 +4x+32=136 \\ 6x+40 =136 \\ 6x=96 \\ x =16 hours [/tex]
So Issac worked for 16 hours, Ruby worked for 24 hours and Svetlana worked for 24 times 4 equals 96 hours .
