Lesson 124 of Doodles Do Algebra

lesson124doodleboyToday’s exercise is to learn to recognize and translate a word problem into 3 independent equations with 3 unknowns, or 4 equations and 3 unknowns. As a bonus, and for practice your child gets to pick one of the two problems and solve it all the way after writing down the equations.

Download Lesson 124 of Doodles Do Algebra HERE


1. First equation: x+y+z=59

Second equation: y-x=5

Third equation: z-x=9

Solution: rewrite second equation in terms of y equals something and the third equation in terms of z equals something. Then plus those both into the first equation and solve for x. Then plug that value of x into the second equation to solve for y and into the third equation to solve for z and you are done.


First equation: 2r+5c=12 where r is price of one roll and c is price of one cookie.

Second equation: 3c+5l=18 where c is price of one cookie and l is price of one loaf of bread.

Third equation: 4c+5p=28 where c is price of one cookie and p is price of one pretzel.

Fourth equation: 5l+6p=?

Since I did not include the cost of the final trip to the store, you do not have 4 independent equations and 4 unknowns, only 3 equations and 4 unknowns. This is not a solvable problem, so if your child points that out then give her a gold star and lots of praise!