Question 150247
----"Luisa is 5 years younger than her sister Sigrid"----


Luisa=L
Sigrid=L+5


----"8 years from now she will be four-fifths as old as her sister will be then"----


L+8=4/5(L+5+8)


Combine like terms on the right side
L+8=4/5(L+13)


Distribute on the right side
L+8=4/5L+10.4


Subtract 8 from both sides
L=4/5L+2.4


Subtract 4/5L from both sides
1/5L=2.4


Multiply both sides by 5
L=12


Luisa=L
Sigrid=L+5


----"How old is each now?"----


Louisa=12
Sigrid=17