Christy correctly answer 85% of the questions on her math test if she missed 6 problems how many questions were there on the test?

Let total number of questions be x.

If she answered 85% correctly, than that means she answered 15% incorrectly.

You can set up the equation 15% (0.15) of total number of questions (x) equals 6.
0.15*x = 6
x = 40

There were 40 questions on the test.