Devi and her brother had the same amount of money. after devi spent 2/5 of her money and her brother spent 3/10 on his money, they had 78$ left altogether. how much money did they spend altogether?

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.

the 3rd option is right

step-by-step explanation:

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