Jordan eats cereal 3 out of 4 days. she used the equation to predict c, the number of days she would eat cereal in 36 days. what value of c would make this equation true

This is the concept of algebra. Let the ratio of days she uses to eat serial be:
3 out 4, this will give us:
3/4
this means she eats cereal 3/4 out of every time she eats.
Therefore the number of time out of x times she eats cereals will be:
c=3/4x
where x is the number of days.
Therefore the number of times she would eat cereals out of 36 will be:
c=3/4×36
c=27