David and robort have 120 baseball cards.David gives robort one third of his cards and then 10 more cards.Robort now has five times as many cards David.How many cards robort have originally

Answer 1

David gave Robert D/3 + 10
now David has D - D/3 - 10
Robert has R + D/3 + 10
so
R + D/3 + 10 = 5 (D - D/3 -10)
3 R + D + 30 = 15 D - 5 D - 150
3 R - 9 D = - 180
R - 3 D = - 60
but we know R+D = 120
so
R + D =120
R - 3 D = -60
-----------------subtract
4 D = 180
D = 45
R = 120 - 45 = 75

Answer 2

David has x cards.
x-x/3-10 = 2x/3-10 left.
2x/3-10 + 5(2x/3-10) = 120
2x/3-10(1+5) = 120
2x/3-10 = 20
2x/3 = 30
X = 45 cards.
Robert had120-45 = 75 cards, originally.