# Lesson 125 of Doodles Do Algebra

Today your child will learn about a special case of solving for 2 unknowns: when you are given the sum and the difference between two numbers.

DoodlePoodle explains the process very well on the worksheet so I will not go into the details here.

1. In this problem we help get your child started by setting up the two equations that come from the word problem.

The equations are

$x+y=100$

$x-y=25$

and when you solve for the unknowns, you get x=62.5 and y=37.5

2. The equations are

$x+y=5.5$

$x-y=0.75$

and when you solve for the unknowns, you get x=3.125 and y=2.375 (you can just as well do these problems as fractions instead of as decimals)