2/5 of Joe's savings is equal to 1/4 of Charlie's savings. Express Charlie's savings as a fraction of the total savings of the two boys.
J = Joe's savings
C = Charlie's savings
2/5 of Joe's savings is equal to 1/4 of Charlie's savings means:
2 J / 5 = C / 4
Cross multiply
8 J = 5 C
Divide bith sides by 8
J = 5 C / 8
The total savings of the two boys:
J + C = 5 C / 8 + C =
5 C / 8 + 8 C / 8 = 13 C / 8
Charlie's savings as a fraction of the total savings of the two boys:
C / (J + C) = C / ( 13 C / 8 ) =
8 C / 13 C = 8 / 13