Step-by-step explanation:
Let the amount mary and jane had be 2x and x respectively.
Let the equal amount be y:
Using the simultaneous equation method, multiply the first equation by the coefficient of x(1) of the second equation and the second equation by the coefficient of x(2) of the first equation:
Subtract the second equation from the first equation:
$320 was their equal amount.
Substitute 320 for y in any equation:
Therefore, Jane had $560 at first and Mary had $1120 at first.