Josiah, Gerald and Marcus had a total of 1280 stamps in their collection. Josiah gave away 2/5 of his stamp collections. Gerald gave away 120 stamps and Marcus gave away twice as many stamps as Josiah. In the end, they had 740 stamps left. How many stamps did Gerald and Marcus have altogether in the end?
J + G + M = 1280
J still has 3/5 J
G still has ( G - 120)
M still has M- 4/5 J
3/5 J + (G-120) + (M-4/5 J) = 740
in the end we want (G-120) + (M-4/5 J)