Mrs Li is x years old Mr Li is 6 years older than Mrs Li. David is one third of Mr Li.

Write an expression in terms of x for Davids age and the Sum of their 3 ages giving your answer in simplest form.

Mrs. Li: x

Mr. Li: 6+x

David: the word "of" means multiplication so

1/3 * (6+x)

Sum: x+6+x+1/3 * (6+x)

Multiplication first, so = x+6+x+2+x/3

Combine like terms: (x+x+x/3) + (6+2)

Find common denominator : (3x+3x+x) / 3 + 8

Simplify : 7x/3 + 8