So we're given that D biked 11 times as many miles as K. If we were to look at the amount of miles both people biked as values, would you say that D's value of miles biked is 11 times more than K's value? As in K's value of miles biked would have to be multiplied by 11 in order to get the same exact value as D's value? Therefore, we can assume this:

D = 11K

We're also given that the total miles biked is 156, so we have to add the values of both bikers and set it equal to 156, and since we found out that D = 11K, we can plug that in for D.

D + K = 156

11K + K = 156

12K + 156

Solving this out, we will get:

12K/12 = 156/12

K = 13

So we know that K biked 13 miles last month. But the question asks for the amount that D biked. So we can use the equation D = 11K to figure it out

D = 11K

D = 11(13)

D = 143.

**Therefore, D biked 143 miles last month**.