Sipho is 4 older than his sister, their combined age is 18. How old is sipho

Answer 1

sister ---- x
Sipho ---- x+4
" their combined age is 18" , what does "combined" insinuate ?
Form the resulting equation and solve for x

Answer 2

s + s + 4 = 18

2s = 14

s = 7 (sister's age)