(a)
pavan saves = x
his 1st brother saves = x + 4
2nd brother saves = x +4
all together they save = x + x +4 + x + 4
= 3x+8
so
3x + 8 = 26
(b)
3x + 8 = 26
subtract 8 from.both side
3x + 8 - 8 = 26 - 8
3x = 18
divide by 3 both side
3x/3 = 18/3
x = 6
so pavan saves $ 6 each month