Jane is seven years older than amy. twelve years ago, amy was half as old

as jamie is now. how old is jamie now?

J=jane's age now

a=amy's age now

a-12=amy's age 12 years ago

j is 7 older than a

j=7+a

12 years ago

amy was 1/2 as old as jamie is now

a-12 = (1/2) j

so

j=7+a

sub 7+a for j

a-12 = (1/2) (7+a)

times 2 both sides

2a-24=7+a

minus a both sides

a-24=7

add 24 both sides

a=31

j=7+a

j=7+31

j=38

jamie is 38 now

Jane+7=amy's age

7x2=14 14/2=7

j14=a7

amy - 7 + 12years = 19years now