This year, jake is 5 years older than his sister. three years ago, jake was twice his sister's age. how old is jake's sister now?
assign two variables and equations. solve.

J=jakes agenow
s=sister's age now

j is 5 more than sister
j=5+s

3 years ago (j-3 and s-3)
jake was 2 times sister
(j-3)=2(s-3)
find s

distribute
2(s-3)=2s-6

now we have
j-3=2s-6
we have
j=5+s
subsitute that (subsitute 5+s for j)
5+s-3=2s-6
add like terms
s+2=2s-6
subtract s from both sides
2=s-6
add 6 to both sides
8=s
his sister is 8 yeasr old