Erika and Fanny have $255. Mary and Erika have $312. The ratio of Fanny to Mary is 4 : 7. How much does Erika have?
Amount that Fanny has = 4 u
Amount that Mary has = 7 u
The amount that Erika has is the repeated identity.
Erika + 4 u = 255 --- (1)
Erika + 7 u = 312 --- (2)
(2) - (1)
7 u - 4 u = 312 - 255
3 u = 57
1 u = 57 ÷ 3 = 19
From (1):
Erika + 4 u = 255
Erika + 4 x 19 = 255
Erika + 76 = 255
Amount that Erika has
= 255 - 76
= $179
Answer(s): $179
