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Cogito

Grade 8 Math · Chapter 5 · Lesson 3

Practice Worksheet

Solving a System by Elimination

Add the equations and one letter disappears.

10 problems · about 20 minutes · 8.EE.C.8

NameDate

Figure — use these to answer the problems

Whichever method is used, the answer is where the lines cross.
-10-10-5-5551010
y = −x + 7
Slope-1
Intercept7
Figure 1

Warm-Up Review

From earlier lessons. Loosen up before the new work.

3 problems

  1. From “Solving a System by Substitution”

    y = 4x and x + y = 15. What is x?

    Answer

  2. From “Where Two Lines Meet”

    y = 5x and y = 3x + 8. What is x?

    Answer

  3. From “Writing Equations from Situations”

    6 + 5m = 3m + 20. What is m?

    Answer

Warm Up

Straightforward practice. Get the method working first.

3 problems

  1. x + y = 12 and x − y = 4. What is x?

    Answer

  2. x + y = 9 and x − y = 3. What is x?

    Answer

  3. Same system. What is y?

    Answer

Build It Up

The same ideas with more to keep track of.

2 problems

  1. 2x + y = 11 and x + y = 7. What is x?

    Answer

  2. Same system. What is y?

    Answer

Stretch Yourself

Mixed problems. Work out what kind of question it is before you start.

2 problems

  1. The Sum

    x + y = 10 and x − y = 2. What is x?

    Answer

  2. The Other

    Same system. What is y?

    Answer