Question

Ann has 30% less money than mary and jess has 70% more money than Mary. If the threee of them have a total of 102$, how much money does each girl have individually?

Answer 1

You need to make a system of three equations with three unknowns that suits the problem to know how many dollars each one has. Then, let's call:
x = Ann's money amount
y = Amount of Mary's money.
z = Amount of Jess's money.
Solving the system of equations, the answers are:
x = 21 $, y = 30 $, z = 51 $.
I attach the solution.

Answer 2

Let x be the amount of Ann money, y be Jessica's money and z Mary money. 30% of z equates 0.3*z. Ann has 30% less than z so: x = z - 0.3z = 0.7z.70% of z equates 0.7z. "Jessica has 70% more than Mary " we deduce the equation: y =z+0.7z= 1.7z.Signe the total is $102, we deduce the equation x+y+z = 102. x=0.7z and y=1.7z then 0.7z+1.7z+z=102, therefore 3.4z=102 then z =102/3.4 = $30.x=0.7*30= 21 and y=1.7*30=51.
Ann has $21, Mary has $30 and Jessica has $51.