a) Let $x be the total amount the father gave them at first...
Yani took 3/4 of it, so Yani will have 0.75x and zul will have 0.25x .
After Yani saved $120 and Zul spent $80, the ratio of their savings (Zul:Yani) became 1:5.This means that Yani’s new saving is 5 times more than Zul’s new saving.So.....
(0.75x+120)/(0.25x-80)=5
Solve for x....
0.75x+120=1.25x-400
0.5x=520
x=$1040(total amount that father give)
Zul’s saving in the end =0.25x-80=0.25(1040)-80=$180(answer)

b)Amount that Yani has at first =0.75x=0.75(1040)=$780(answer)