Question

The sum of liz's and melinda's ages is 28. if liz was 1/3 melinda's age 6 years ago, how old will liz be next year?

Answer 1

The first thing we must do for this case is to define variables:
 We have then:
 x: liz's age
 y: melinda's age
 We now write the system of equations:
 $x + y = 28 x-6 = (1/3) (y-6)$
 By solving the system graphically we have that the age of each one is currently:
 $x = 10 y = 18$
 Next year, the age of liz is:
 $x + 1 = 10 + 1 = 11$
 Answer:
 Next year, Liz's age is 11 years.
 Note: see attached image for the graphic solution.