Ten years ago Ade's age was half the age of his sister, today Ade is 12yrs old. how old is his sister?
+36915 Ade's age 10 years ago = A
and this was 1/2 the age of his sister A = 1/2 S
10 years later Ade is now A + 10 =12 substitute in the red equation above
A + 10 = 12
1/2 S + 10 = 12
S=4 (remember this was 10 years ago)
and sister is S + 10 = 4+ 10 = 14 y/o Sister's age now
