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