Question 304397
Herman is half as old as his sister.
h = {{{1/2}}}s
or
s = 2h
:
 In seven years he will be two-thirds his sister's age.
h + 7 = {{{2/3}}}(s + 7)
Multiply both sides by 3
3(h+7) = 2(s + 7)
3h + 21 = 2s + 14
3h = 2s + 14 - 21
3h = 2s - 7
Replace s with 2h
3h = 2(2h) - 7
3h = 4h - 7
7 = 4h - 3h
h = 7 is Herman's present age
:
:
Check solution, s = 2(7) = 14 is sister's age
"In seven years he will be two-thirds his sister's age.
7 + 7 = {{{2/3}}}(14 + 7)
14 = {{{2/3}}}(21)