Back to Solve systems of linear equations — Problem 3 · Task Set 41

HSA.REI.C.6 Tutor Intake — Systems of Linear Equations

This short check helps your tutor understand where to start. Answer each question without help. If you are not sure, give your best try — the goal is to find what to work on together, not to grade you.

Grade 9·8 problems·~13 min·Common Core Math - HS Algebra·standard·hsa-rei-c-6

Work through problems with immediate feedback

Procedures

After using elimination on a system, a student finds $y = 3$ . They
now need to find $x$ .

The original system was:
$E_1: 5x - 2y = 4$
$E_2: 3x + 4y = 30$

During elimination, the student multiplied $E_1$ by 2 to get $E_1': 10x - 4y = 8$ .
They then added $E_1'$ and $E_2$ to get $13x = 38$ , giving $x = \frac{38}{13}$ .

Where should the student substitute $y = 3$ to find $x$ ?

Into the modified equation $E_1'$ : $10x - 4y = 8$

Into $13x = 38$ (the equation obtained by adding $E_1'$ and $E_2$ )

Into either original equation ( $E_1$ or $E_2$ )

Into the average of $E_1$ and $E_2$