Given:
The monthly phone cost C can be represented by this equation:
[tex]C=12+a\cdot m[/tex]
where, a is the additional charge per minute, and m is the number of minutes used.
To find:
The equation can be used to find the number of minutes a customer used if we know and a and C.
Solution:
We have,
[tex]C=12+a\cdot m[/tex]
We need to isolate m on one side.
Subtract 12 from both sides.
[tex]C-12=a\cdot m[/tex]
Divide both sides by a.
[tex]\dfrac{C-12}{a}=\dfrac{a\cdot m}{a}[/tex]
[tex]\dfrac{C-12}{a}=m[/tex]
[tex]m=\dfrac{C-12}{a}[/tex]
The options are not in proper format.
Therefore, the required equation is [tex]m=\dfrac{C-12}{a}[/tex].
