If x=21 then y=49. What is the value of x when y=56?

24

Step-by-step explanation:

set them up as a fraction.

21/49=x/56

cross multiply: 21*56=49x

1176=49x

divide both sides by 49

x=24

28

Step-by-step explanation:

notice that when x=21 thats 3x7=21  

then when y=49  thats 7x7  

so when y=56  that's 8x7

notice there is a patter of 7 being used?   there are probably a lot of other patterns that would also work.. but.  if your class is working on multiplying by 7 , then this is probably the right pattern.  

from the above pattern, then,

x=4x7 when y=56

x=28

which expression represents the approximate length of bc?

step-by-step explanation:

it's undefined because anything multiplied by 0 is 0. that said, 7 days is 168 hours