Need help with this math problem

Answer:
A)
Step-by-step explanation:
Given expression:
[tex] \boxed{\mathsf{c = 15 + am}}[/tex]
subtracting 15 from both sides, and combining like terms on the RHS
[tex] \implies\mathsf{c - 15 = (15 - 15)+ am}[/tex]
Dividing both sides by a
[tex] \implies\mathsf{ \frac{c - 15}{a} = am \times \frac{1}{a} }[/tex]
a On the RHS gets canceled for being present in both Numerator as well as denominator, and were left with the following equation:
[tex] \implies\mathsf{ \frac{c - 15}{a} = m }[/tex]