Suppose c varies directly as m. if c=56 when m=8 find c when m=3

56 8
x3
x=56*3/8=21

it can be done also like this:
c=km
56=k*8
k=56/8=7

c=7m , so c= 7*3=21

The ratio 56 to 8 can be written as a fraction:

56/8

This simplifies to 7. Because C varies directly with M, we can use the second value of M to write an equivalent algebraic expression.

c/3 = 7

Multiply both sides by 3:

c = 21

When M = 3, C = 21

I hope this helps!

What's the denominator

The answer would be (c)