maths~~~!!!!

The ratio of the number ofmarbles owned by Susan to the number of marbles owned by Teresa is 5:2 . Susanhas N marbles . If Susan gives 18 of her own marbles to Teresa , both of themwill have the same amount of marbles . Find N


Number of marbles owned by Susan = N
Number of marbles owned by Teresa = (2/5)N = 2N/5

N - 18 = (2N/5) + 18
N - (2N/5) = 36
3N/5 = 36
N = 36 * (5/3)
N = 60

2011-09-05 01:57:18 補充：
Susan has N marbles, and gives 18 marbles to Teresa. Then, she has (N - 18) marbles.

Teresa has 2N/5 marbles, and gets 18 marbles from Susan. Then, she has [(2N/5) + 18] marbles.

After Susan gives 18 marbles to Teresa,they have the same number of marbles :
N - 18 = (2N/5) + 18