Question 76006
Let f = fred's age now. b = brother's age now
:
Write an equation for each sentence:
"Frederique is 2 years older than her brother."
f = (b + 2)
or
b = (f - 2)
:
" 12 years ago she was twice as old as he was."
(f - 12) = 2(b - 12)
  f - 12 = 2b - 24
f = 2b - 24 + 12
f = 2b - 12
:
Substitute (f-2) for b:
f = 2(f - 2) - 12
f = 2f - 4 - 12
f - 2f = -16
-f = -16
f = 16 yrs age now, then b = 16 - 2 = 14 yrs age now
:
:
Check 12 years ago
(16-12) = 2(14-12)
4 = 2(2)