Given the task definition and input, reply with output. In this task you are given a list of numbers and you need to find the average of each two consecutive values. The average of two numbers a and b is calculated as: (a + b) /2. The output should be a list of the averages of each two consecutive values. A list is presented with two brackets and comma-separated values, like: [1,2,3].

[-87, 35, 61, 30, 47, 12, 80, -16, 72, -64, 54, 13, 97, 42, -21]

[-26.0, 48.0, 45.5, 38.5, 29.5, 46.0, 32.0, 28.0, 4.0, -5.0, 33.5, 55.0, 69.5, 10.5]