Math
posted by Lisa on .
Ricky wrote the following to show that his sister's age is 6 yrs. less than 3 times his age. Explain what he did wrong.
Give the correct expression Let a stand for my age My sister's age a/36

ricky's age
sister's age:
6 less than 3 times rick's age > 3a  6
I would never ask for an "explanation" of somebody's illogical thinking 
Richard is 6 years older than Lisa, and in 5 years the sum of their ages will be twice as much as the sum of their ages 4 years ago. Find their present ages.