Question

When using substitution, choose the best choice that describes a possible first step in solving

the following system of equations.
3x – 6y = -12
2x + y = 12
A. ADD (y) to both sides in the bottom equation
B. MULTIPLY the top equation by (-6)
C. SUBTRACT (2x) from both sides in the bottom equation
D. DIVIDE the top equation by (3)
E. SUBTRACT (-6y) to both sides of the top equation

Answer 1

C. SUBTRACT (2x) from both sides in the bottom equation

Explanation:

Given

`3x - 6y = -12`

`2x + y = 12`

Required

The first step of a substitution method

In the second equation, notice that the coefficient of y is 1.

So, the first step is to make y the subject of the formula.

This is achieved by subtracting 2x from both sides of the equation.

`2x + y = 12`

`2x - 2x + y = 12 - 2x`

`y = 12 - 2x`

Hence: (c) is true