Let us assume Devi or her brother amount = $x.
Devi spent 2/5 of x, that is 2/5 x.
Remaining amount of Devi = x- 2/5 x = 5x/5 - 2x/5 = 3x/5.
Her brother spent 3/10 of x, that is 3/10 x.
Remaining amount of her brother = x- 3/10 x = 10x/10 - 3x/10 = 7x/10.
Total amount they left together = $78.
Therefore,



Multiply equation by LCM 10.






Therefore, each one spent $60 and they spent altogether = 60+60 = $120.